feat: Spot 3회 median + Placement 가이드 딜레이 3초

Spot:
- 1회 즉시 → 3회 연속 측정(200ms 간격) → median 표시
- 측정 중 로딩 인디케이터
- 2회 이상 유효 시 median 적용

Placement:
- 가이드 텍스트 최소 유지시간 4초 → 3초

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -3,6 +3,8 @@ package com.example.medilightv2android.ui.views.monitoring
 import android.os.Handler
 import android.os.Looper
 import android.util.Log
+import androidx.compose.runtime.rememberCoroutineScope
+import kotlinx.coroutines.launch
 import com.example.medilightv2android.AppScreen
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.foundation.Canvas
@@ -817,24 +819,47 @@ fun PiezoMonitoringView(appState: AppState) {
                     }
                 }
 
-                // Spot (single measurement, 1.5초 쿨다운)
+                // Spot (3회 측정 → median)
                 var spotCooldown by remember { mutableStateOf(false) }
+                var spotInProgress by remember { mutableStateOf(false) }
+                val spotScope = rememberCoroutineScope()
                 Button(
                     onClick = {
-                        if (!isMeasuring && !isAutoMeasuring && !spotCooldown) {
-                            measure()
+                        if (!isMeasuring && !isAutoMeasuring && !spotCooldown && !spotInProgress) {
+                            spotInProgress = true
                             spotCooldown = true
-                            handler.postDelayed({ spotCooldown = false }, 1500)
+                            spotScope.launch {
+                                val spotResults = mutableListOf<Double>()
+                                repeat(3) {
+                                    measure()
+                                    while (isMeasuring) { kotlinx.coroutines.delay(100) }
+                                    if (lastVolumeMl > 0) spotResults.add(lastVolumeMl)
+                                    kotlinx.coroutines.delay(200)
+                                }
+                                if (spotResults.size >= 2) {
+                                    spotResults.sort()
+                                    val median = spotResults[spotResults.size / 2]
+                                    lastVolumeMl = median
+                                    maxVolumeMl = maxOf(maxVolumeMl, median)
+                                    Log.d("PiezoMonitor", "SPOT median=${"%.1f".format(median)}ml from ${spotResults.map { "%.0f".format(it) }}")
+                                    val maxVol = appState.piezoSettings.maxVolume.toDouble()
+                                    val pct = if (maxVol > 0) (median / maxVol).coerceAtMost(1.0) else 0.0
+                                    val level = (pct * BladderLevel.MAX_LEVEL).toInt().coerceIn(1, BladderLevel.MAX_LEVEL)
+                                    appState.bladderLevel = appState.bladderLevel.copy(currentLevel = level)
+                                }
+                                spotInProgress = false
+                                handler.postDelayed({ spotCooldown = false }, 1000)
+                            }
                         }
                     },
-                    enabled = !isMeasuring && !isAutoMeasuring && !spotCooldown,
+                    enabled = !isMeasuring && !isAutoMeasuring && !spotCooldown && !spotInProgress,
                     modifier = Modifier.weight(1f).height(56.dp),
                     shape = RoundedCornerShape(14.dp),
                     colors = ButtonDefaults.buttonColors(
                         containerColor = urgency.gradientColors.first()
                     )
                 ) {
-                    if (isMeasuring && !isAutoMeasuring) {
+                    if (spotInProgress) {
                         CircularProgressIndicator(color = Color.White, modifier = Modifier.size(18.dp), strokeWidth = 2.dp)
                     } else {
                         Text("Spot", fontSize = 13.sp, fontWeight = FontWeight.SemiBold, color = Color.White)

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

@@ -545,7 +545,7 @@ fun PlacementGuideView(appState: AppState) {
 
                         val now = System.currentTimeMillis()
                         val elapsed = now - lastHintChangeMs
-                        if ((debounceCount >= 2 && elapsed >= 4000) || guideResult.isPass) {
+                        if ((debounceCount >= 2 && elapsed >= 3000) || guideResult.isPass) {
                             directionHint = guideResult.hint
                             directionIcon = guideResult.icon
                             placementScore = guideResult.score