fix(dev): 슬라이더 변경이 앱 재시작 시 사라지던 문제 — SharedPreferences 영속화

증상: Dev settings 의 walking/posture 임계 슬라이더를 조정해도 다음 앱 실행
      시 default 로 리셋. 사용자: "save해도 변경이 안되는 것 같음".

원인: GreenZoneConstants 의 임계들은 @Volatile var (메모리 변수). 슬라이더가
      즉시 값을 GreenZoneConstants 에 쓰지만 SharedPreferences 등 영속
      저장소엔 안 들어감 → 앱 재시작 시 default 로 다시 초기화.

수정:
  1) PostureTuningPrefs.kt 신규
     - loadAll(context): SharedPreferences → GreenZoneConstants 로드
     - saveAll(context): 현재 GreenZoneConstants → SharedPreferences 저장
     - resetAll(context): defaults 로 복원
     - 11개 키 (pitch lying / acc min/max / poll ms / walking 7개)

  2) PiezoMonitoring LaunchedEffect(Unit) 에서 loadAll 호출
     - 앱 진입 시 저장된 사용자 튜닝 값 자동 로드

  3) 11개 slider 모두 onValueChange 마지막에 saveAll 호출
     - 슬라이더 변경 즉시 영속 저장 (별도 save 버튼 불필요)

  4) Reset Thresholds 버튼 추가 (Verification 섹션 위)
     - resetAll 호출 → defaults 로 복원 + prefs 저장
     - Toast 로 안내 ("close & reopen Settings to refresh sliders" —
       slider 의 remember state 는 reopen 해야 갱신됨)

테스트:
  1. Dev settings → Start Wmean = 25 변경 → 앱 종료
  2. 앱 재실행 → Dev settings 다시 열기 → Start Wmean = 25 유지 확인 ✓
  3. 분류기도 25 값으로 동작

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/src/main/java/com/example/medilightv2android/services/PostureTuningPrefs.kt

@@ -0,0 +1,80 @@
+/*
+ * PostureTuningPrefs — Posture / Walking detector 임계값 SharedPreferences 영속화.
+ *
+ * GreenZoneConstants 의 임계값들은 @Volatile var (메모리) 라 앱 재시작 시 default 리셋.
+ * 사용자가 dev slider 로 튜닝한 값을 유지하려면 prefs 에 저장 + 시작 시 로드.
+ *
+ * 사용:
+ *   loadAll(context) — 앱/화면 시작 시 한 번 호출 → SharedPreferences 값 → GreenZoneConstants
+ *   saveAll(context) — slider 변경 시 호출 → 현재 GreenZoneConstants → SharedPreferences
+ *   resetAll(context) — 사용자가 reset 누름 → defaults 로 복원
+ */
+package com.example.medilightv2android.services
+
+import android.content.Context
+import com.example.medilightv2android.managers.GreenZoneConstants
+
+object PostureTuningPrefs {
+
+    private const val PREF = "posture_tuning_prefs"
+
+    // Defaults — GreenZoneConstants 의 초기값과 일치 유지
+    private const val D_PITCH_LYING = 25f
+    private const val D_ACC_MIN = 0.8f
+    private const val D_ACC_MAX = 1.2f
+    private const val D_POLL_MS = 1000L
+    private const val D_WALK_PITCH = 45f
+    private const val D_WALK_START_WMEAN = 15f
+    private const val D_WALK_START_WSTD = 2f
+    private const val D_WALK_KEEP_WMEAN = 2f
+    private const val D_WALK_START_HOLD_MS = 6000L
+    private const val D_WALK_KEEP_HOLD_MS = 2000L
+    private const val D_WALK_WINDOW_MS = 1500L
+
+    fun loadAll(context: Context) {
+        val p = context.applicationContext.getSharedPreferences(PREF, Context.MODE_PRIVATE)
+        GreenZoneConstants.pitchLyingThreshold   = p.getFloat("pitchLying", D_PITCH_LYING)
+        GreenZoneConstants.postureAccMagMin      = p.getFloat("accMin", D_ACC_MIN)
+        GreenZoneConstants.postureAccMagMax      = p.getFloat("accMax", D_ACC_MAX)
+        GreenZoneConstants.posturePollIntervalMs = p.getLong("pollMs", D_POLL_MS)
+        GreenZoneConstants.walkingMinPitchDeg    = p.getFloat("wPitch", D_WALK_PITCH)
+        GreenZoneConstants.walkingStartWmean     = p.getFloat("wStartWmean", D_WALK_START_WMEAN)
+        GreenZoneConstants.walkingStartWstd      = p.getFloat("wStartWstd", D_WALK_START_WSTD)
+        GreenZoneConstants.walkingKeepWmean      = p.getFloat("wKeepWmean", D_WALK_KEEP_WMEAN)
+        GreenZoneConstants.walkingStartHoldMs    = p.getLong("wStartHoldMs", D_WALK_START_HOLD_MS)
+        GreenZoneConstants.walkingKeepHoldMs     = p.getLong("wKeepHoldMs", D_WALK_KEEP_HOLD_MS)
+        GreenZoneConstants.walkingWindowMs       = p.getLong("wWindowMs", D_WALK_WINDOW_MS)
+    }
+
+    fun saveAll(context: Context) {
+        context.applicationContext.getSharedPreferences(PREF, Context.MODE_PRIVATE).edit().apply {
+            putFloat("pitchLying", GreenZoneConstants.pitchLyingThreshold)
+            putFloat("accMin", GreenZoneConstants.postureAccMagMin)
+            putFloat("accMax", GreenZoneConstants.postureAccMagMax)
+            putLong("pollMs", GreenZoneConstants.posturePollIntervalMs)
+            putFloat("wPitch", GreenZoneConstants.walkingMinPitchDeg)
+            putFloat("wStartWmean", GreenZoneConstants.walkingStartWmean)
+            putFloat("wStartWstd", GreenZoneConstants.walkingStartWstd)
+            putFloat("wKeepWmean", GreenZoneConstants.walkingKeepWmean)
+            putLong("wStartHoldMs", GreenZoneConstants.walkingStartHoldMs)
+            putLong("wKeepHoldMs", GreenZoneConstants.walkingKeepHoldMs)
+            putLong("wWindowMs", GreenZoneConstants.walkingWindowMs)
+            apply()
+        }
+    }
+
+    fun resetAll(context: Context) {
+        GreenZoneConstants.pitchLyingThreshold   = D_PITCH_LYING
+        GreenZoneConstants.postureAccMagMin      = D_ACC_MIN
+        GreenZoneConstants.postureAccMagMax      = D_ACC_MAX
+        GreenZoneConstants.posturePollIntervalMs = D_POLL_MS
+        GreenZoneConstants.walkingMinPitchDeg    = D_WALK_PITCH
+        GreenZoneConstants.walkingStartWmean     = D_WALK_START_WMEAN
+        GreenZoneConstants.walkingStartWstd      = D_WALK_START_WSTD
+        GreenZoneConstants.walkingKeepWmean      = D_WALK_KEEP_WMEAN
+        GreenZoneConstants.walkingStartHoldMs    = D_WALK_START_HOLD_MS
+        GreenZoneConstants.walkingKeepHoldMs     = D_WALK_KEEP_HOLD_MS
+        GreenZoneConstants.walkingWindowMs       = D_WALK_WINDOW_MS
+        saveAll(context)
+    }
+}

app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt

@@ -712,7 +712,9 @@ fun PiezoMonitoringView(appState: AppState) {
     }
 
     // Posture event 로깅 — 검증용 CSV (앱 진입 시 새 파일)
+    // + 사용자 튜닝 임계값 SharedPreferences 에서 로드
     LaunchedEffect(Unit) {
+        com.example.medilightv2android.services.PostureTuningPrefs.loadAll(context)
         com.example.medilightv2android.services.PostureEventLogger.startSession(context)
     }
 
@@ -1892,7 +1894,8 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(
                             value = pitchThrVal,
-                            onValueChange = { pitchThrVal = it; GreenZoneConstants.pitchLyingThreshold = it },
+                            onValueChange = { pitchThrVal = it; GreenZoneConstants.pitchLyingThreshold = it
+                                com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context) },
                             valueRange = 10f..70f,
                             steps = 11,
                             colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary)
@@ -1968,6 +1971,7 @@ fun PiezoMonitoringView(appState: AppState) {
                             onValueChange = {
                                 pollIntervalVal = it
                                 GreenZoneConstants.posturePollIntervalMs = (it * 1000).toLong()
+                                com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                             },
                             valueRange = 1f..15f,    // 1초 ~ 15초
                             steps = 0,
@@ -1987,6 +1991,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkPitchVal, onValueChange = {
                             walkPitchVal = it; GreenZoneConstants.walkingMinPitchDeg = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 20f..70f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkStartWmean by remember { mutableStateOf(GreenZoneConstants.walkingStartWmean) }
@@ -1997,6 +2002,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkStartWmean, onValueChange = {
                             walkStartWmean = it; GreenZoneConstants.walkingStartWmean = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 1f..20f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkStartWstd by remember { mutableStateOf(GreenZoneConstants.walkingStartWstd) }
@@ -2007,6 +2013,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkStartWstd, onValueChange = {
                             walkStartWstd = it; GreenZoneConstants.walkingStartWstd = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.5f..10f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkKeepWmean by remember { mutableStateOf(GreenZoneConstants.walkingKeepWmean) }
@@ -2017,6 +2024,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkKeepWmean, onValueChange = {
                             walkKeepWmean = it; GreenZoneConstants.walkingKeepWmean = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.5f..30f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         // Walking 시간 변수 (sec)
@@ -2028,6 +2036,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkStartHold, onValueChange = {
                             walkStartHold = it; GreenZoneConstants.walkingStartHoldMs = (it * 1000).toLong()
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.2f..5f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkKeepHold by remember { mutableStateOf(GreenZoneConstants.walkingKeepHoldMs / 1000f) }
@@ -2038,6 +2047,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkKeepHold, onValueChange = {
                             walkKeepHold = it; GreenZoneConstants.walkingKeepHoldMs = (it * 1000).toLong()
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.5f..10f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkWindow by remember { mutableStateOf(GreenZoneConstants.walkingWindowMs / 1000f) }
@@ -2048,6 +2058,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = walkWindow, onValueChange = {
                             walkWindow = it; GreenZoneConstants.walkingWindowMs = (it * 1000).toLong()
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.5f..5f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         HorizontalDivider(modifier = Modifier.padding(vertical = dividerPadding))
@@ -2063,6 +2074,7 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = accMagMin, onValueChange = {
                             accMagMin = it; GreenZoneConstants.postureAccMagMin = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 0.3f..1.0f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var accMagMax by remember { mutableStateOf(GreenZoneConstants.postureAccMagMax) }
@@ -2073,10 +2085,27 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         Slider(value = accMagMax, onValueChange = {
                             accMagMax = it; GreenZoneConstants.postureAccMagMax = it
+                            com.example.medilightv2android.services.PostureTuningPrefs.saveAll(context)
                         }, valueRange = 1.0f..3.0f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         HorizontalDivider(modifier = Modifier.padding(vertical = dividerPadding))
 
+                        // Reset to defaults — 모든 threshold 를 default 로 복원 + prefs 저장.
+                        OutlinedButton(
+                            onClick = {
+                                com.example.medilightv2android.services.PostureTuningPrefs.resetAll(context)
+                                android.widget.Toast.makeText(context,
+                                    "Defaults restored — close & reopen Settings to refresh sliders",
+                                    android.widget.Toast.LENGTH_LONG).show()
+                            },
+                            modifier = Modifier.fillMaxWidth(),
+                            colors = ButtonDefaults.outlinedButtonColors(contentColor = Color(0xFFE53935))
+                        ) {
+                            Text("Reset Thresholds to Defaults", fontSize = 13.sp, fontWeight = FontWeight.SemiBold)
+                        }
+
+                        HorizontalDivider(modifier = Modifier.padding(vertical = dividerPadding))
+
                         // Verification annotation buttons — ground truth marker.
                         // 누르는 순간 timestamp 가 CSV 에 ANNOTATION row 로 기록 → 알고리즘 detection 과 대조.
                         // 파일: Downloads/VesiScan_Posture/yyyy-MM-dd_HHmmss.csv