feat(locale): Phase 1 — 언어 전환 인프라 (시스템/한국어/English)

신규:
- LocalePref.kt — Mode {SYSTEM, KO, EN} 영속화 + Context wrap
- MainActivity.attachBaseContext — 사용자 선택 locale 으로 Configuration override
- HomeView 우상단 🌐 Language 아이콘 → 선택 다이얼로그 → recreate

Phase 2: 모든 hardcoded Korean text → strings.xml + values-ko/strings.xml 추출 (대량 작업, 별도 commit)

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

app/src/main/java/com/example/medilightv2android/MainActivity.kt

@@ -43,6 +43,11 @@ import com.example.medilightv2android.ui.views.clinical.ClinicalHomeView
 import com.example.medilightv2android.ui.views.clinical.ClinicalLiveView
 
 class MainActivity : ComponentActivity() {
+    /** 사용자가 선택한 앱 언어 적용 — Activity 생성 전에 Locale wrap. */
+    override fun attachBaseContext(newBase: android.content.Context) {
+        super.attachBaseContext(com.example.medilightv2android.services.LocalePref.wrap(newBase))
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 

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

@@ -0,0 +1,73 @@
+/*
+ * LocalePref — 앱 언어 설정 영속화 + 컨텍스트 wrapping.
+ *
+ * 모드:
+ *   - SYSTEM (default): 폰 시스템 언어 따라감 (Korean → 한국어, 그 외 → English)
+ *   - KO            : 강제 한국어
+ *   - EN            : 강제 영어
+ *
+ * 적용:
+ *   1. MainActivity.attachBaseContext(base) → wrap(base) 호출
+ *   2. 언어 변경 시 setMode(...) 호출 후 activity recreate (또는 process restart)
+ *
+ * Android 13+ 의 per-app locale API (AppCompatDelegate.setApplicationLocales) 와
+ * 무관하게 Configuration override 방식으로 모든 SDK 에서 동작.
+ */
+package com.example.medilightv2android.services
+
+import android.content.Context
+import android.content.res.Configuration
+import android.os.Build
+import java.util.Locale
+
+object LocalePref {
+
+    enum class Mode { SYSTEM, KO, EN }
+
+    private const val PREF = "locale_pref"
+    private const val KEY_MODE = "mode"
+
+    fun getMode(context: Context): Mode {
+        val s = context.applicationContext
+            .getSharedPreferences(PREF, Context.MODE_PRIVATE)
+            .getString(KEY_MODE, Mode.SYSTEM.name) ?: Mode.SYSTEM.name
+        return runCatching { Mode.valueOf(s) }.getOrDefault(Mode.SYSTEM)
+    }
+
+    fun setMode(context: Context, mode: Mode) {
+        context.applicationContext
+            .getSharedPreferences(PREF, Context.MODE_PRIVATE)
+            .edit().putString(KEY_MODE, mode.name).apply()
+    }
+
+    /** 선택된 모드에 맞춰 Locale 적용된 새 Context 반환. attachBaseContext 에서 사용. */
+    fun wrap(base: Context): Context {
+        val mode = getMode(base)
+        if (mode == Mode.SYSTEM) return base   // 시스템 기본 — 손대지 않음
+
+        val locale = when (mode) {
+            Mode.KO -> Locale.KOREAN
+            Mode.EN -> Locale.ENGLISH
+            else -> return base
+        }
+        Locale.setDefault(locale)
+
+        val config = Configuration(base.resources.configuration)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            val list = android.os.LocaleList(locale)
+            android.os.LocaleList.setDefault(list)
+            config.setLocales(list)
+        } else {
+            @Suppress("DEPRECATION")
+            config.locale = locale
+        }
+        return base.createConfigurationContext(config)
+    }
+
+    /** 현재 적용된 locale 의 사용자 표시용 라벨. */
+    fun currentLabel(context: Context): String = when (getMode(context)) {
+        Mode.SYSTEM -> "시스템 기본 / System"
+        Mode.KO -> "한국어"
+        Mode.EN -> "English"
+    }
+}

app/src/main/java/com/example/medilightv2android/ui/views/home/HomeView.kt

@@ -8,9 +8,17 @@ import androidx.compose.foundation.layout.*
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.ui.unit.min
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.RadioButton
+import androidx.compose.material3.RadioButtonDefaults
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Language
 import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
@@ -30,11 +38,23 @@ fun HomeView(appState: AppState) {
     val context = LocalContext.current
     var tapCount by remember { mutableIntStateOf(0) }
     var lastTapTime by remember { mutableLongStateOf(0L) }
+    var showLanguageDialog by remember { mutableStateOf(false) }
+
+    Box(modifier = Modifier.fillMaxSize().background(MlBackground)) {
+        // 우상단 — 언어 설정 진입 아이콘
+        IconButton(
+            onClick = { showLanguageDialog = true },
+            modifier = Modifier
+                .align(Alignment.TopEnd)
+                .padding(8.dp)
+        ) {
+            Icon(Icons.Default.Language, contentDescription = "Language",
+                tint = MlSecondaryText.copy(alpha = 0.7f))
+        }
 
     Column(
         modifier = Modifier
-            .fillMaxSize()
+            .fillMaxSize(),
-            .background(MlBackground),
         horizontalAlignment = Alignment.CenterHorizontally
     ) {
         Spacer(modifier = Modifier.weight(1f))
@@ -139,4 +159,50 @@ fun HomeView(appState: AppState) {
             Spacer(modifier = Modifier.height(48.dp))
         }
     }
+    }  // Box (top-bar gear overlay) close
+
+    // 언어 선택 다이얼로그 — 시스템 / 한국어 / English. 변경 시 Activity recreate.
+    if (showLanguageDialog) {
+        val curMode = com.example.medilightv2android.services.LocalePref.getMode(context)
+        var selected by remember { mutableStateOf(curMode) }
+        AlertDialog(
+            onDismissRequest = { showLanguageDialog = false },
+            title = { Text("Language / 언어") },
+            text = {
+                Column {
+                    listOf(
+                        com.example.medilightv2android.services.LocalePref.Mode.SYSTEM to "시스템 기본 / System default",
+                        com.example.medilightv2android.services.LocalePref.Mode.KO to "한국어",
+                        com.example.medilightv2android.services.LocalePref.Mode.EN to "English",
+                    ).forEach { (mode, label) ->
+                        Row(
+                            verticalAlignment = Alignment.CenterVertically,
+                            modifier = Modifier
+                                .fillMaxWidth()
+                                .clickable { selected = mode }
+                                .padding(vertical = 6.dp)
+                        ) {
+                            RadioButton(
+                                selected = selected == mode,
+                                onClick = { selected = mode }
+                            )
+                            Spacer(Modifier.width(4.dp))
+                            Text(label)
+                        }
+                    }
+                }
+            },
+            confirmButton = {
+                TextButton(onClick = {
+                    com.example.medilightv2android.services.LocalePref.setMode(context, selected)
+                    showLanguageDialog = false
+                    // Activity recreate → attachBaseContext 다시 호출 → 새 locale 적용
+                    (context as? android.app.Activity)?.recreate()
+                }) { Text("OK") }
+            },
+            dismissButton = {
+                TextButton(onClick = { showLanguageDialog = false }) { Text("Cancel") }
+            }
+        )
+    }
 }