feat: Placement Guide 실시간 연속 스캔 (3초 간격)

- 수동 1회 → 자동 반복 스캔 (Start/Stop 토글)
- 3초마다 maa 전송 → Score 실시간 갱신
- 사용자가 센서 움직이면서 점수 변화를 즉시 확인 가능
- "Scanning every 3s — move sensor and watch the score" 안내 문구

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

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

@@ -57,6 +57,7 @@ fun PlacementGuideView(appState: AppState) {
     val analyzer = remember { PiezoEchoAnalyzer.shared }
 
     var isScanning by remember { mutableStateOf(false) }
+    var isContinuousMode by remember { mutableStateOf(false) }
     val channelDetected = remember { mutableStateListOf(false, false, false, false, false, false) }
     val channelUrineLen = remember { mutableStateListOf(0, 0, 0, 0, 0, 0) }
     var directionHint by remember { mutableStateOf("") }
@@ -280,10 +281,9 @@ fun PlacementGuideView(appState: AppState) {
 
             Spacer(modifier = Modifier.height(24.dp))
 
-            // Check Position button
+            // Scan function (reusable)
-            Button(
+            fun performScan() {
-                onClick = {
+                if (isScanning) return
-                    if (!isScanning) {
                 isScanning = true
                 bleManager.piezoCollector.onMultiChannelComplete = { channels ->
                     isScanning = false
@@ -314,41 +314,52 @@ fun PlacementGuideView(appState: AppState) {
                     }
                     lastChannelData = channels
 
-                            // Direction guidance (urineLen-aware)
                     val guideResult = computePlacementGuide(detected, urineLens)
                     directionHint = guideResult.hint
                     directionIcon = guideResult.icon
                     placementScore = guideResult.score
 
-                            // Lock if score >= 70 or 4+ detected
                     if (guideResult.score >= 70 || detected.count { it } >= 4) {
                         isLocked = true
                     }
 
-                            Log.d("PlacementGuide", "Placement: ${detected.count { it }}/6 -- ${
+                    Log.d("PlacementGuide", "Scan #$scanCount: ${detected.count { it }}/6, score=$placementScore%")
-                                detected.mapIndexed { idx, d -> if (d) "CH$idx OK" else "CH$idx X" }.joinToString(" ")
-                            }")
 
-                            // Save placement log
                     logService.logPlacement(
                         channelDetected = detected,
                         direction = directionHint
                     )
                 }
-                        bleManager.piezoCollector.onLog = { msg ->
+                bleManager.piezoCollector.onLog = { msg -> Log.d("PlacementGuide", msg) }
-                            Log.d("PlacementGuide", msg)
-                        }
                 bleManager.sendAllChannels()
             }
+
+            // Continuous scan loop (3초 간격)
+            LaunchedEffect(isContinuousMode) {
+                if (isContinuousMode) {
+                    performScan()
+                    while (isContinuousMode) {
+                        kotlinx.coroutines.delay(3000)
+                        if (isContinuousMode && !isScanning) performScan()
+                    }
+                }
+            }
+
+            // Start/Stop button
+            Button(
+                onClick = {
+                    if (isContinuousMode) {
+                        isContinuousMode = false
+                    } else {
+                        isContinuousMode = true
+                    }
                 },
-                enabled = !isScanning,
                 modifier = Modifier
                     .fillMaxWidth()
                     .height(52.dp),
                 shape = RoundedCornerShape(14.dp),
                 colors = ButtonDefaults.buttonColors(
-                    containerColor = if (isScanning) Color.Gray else MlPrimary,
+                    containerColor = if (isContinuousMode) Color.Red else MlPrimary
-                    disabledContainerColor = Color.Gray
                 )
             ) {
                 if (isScanning) {
@@ -360,13 +371,26 @@ fun PlacementGuideView(appState: AppState) {
                     Spacer(modifier = Modifier.width(8.dp))
                 }
                 Text(
-                    text = if (isScanning) "Scanning..." else "Check Position",
+                    text = when {
+                        isContinuousMode -> "Stop Scanning"
+                        scanCount == 0 -> "Start Scanning"
+                        else -> "Resume Scanning"
+                    },
                     fontSize = 16.sp,
                     fontWeight = FontWeight.SemiBold,
                     color = Color.White
                 )
             }
 
+            if (isContinuousMode) {
+                Text(
+                    "Scanning every 3s — move sensor and watch the score",
+                    fontSize = 11.sp, color = MlSecondaryText,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier.fillMaxWidth()
+                )
+            }
+
             // Start Measurement button (when 4+ channels detected)
             if (isLocked || detectedCount >= 4) {
                 Spacer(modifier = Modifier.height(12.dp))