fix(dev): Walking slider range — Start Hold default(6s)가 max(5)를 초과해 잠겨있던 문제

- Start Hold: 0.2..5 → 0.5..10 (default 6s 정상 표시 + 8~10s 확장 가능)
- Start Wmean: 1..20 → 1..30 (더 strict 한 튜닝 가능)

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

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

@@ -2003,7 +2003,7 @@ 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))
+                        }, valueRange = 1f..30f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkStartWstd by remember { mutableStateOf(GreenZoneConstants.walkingStartWstd) }
                         Row(verticalAlignment = Alignment.CenterVertically) {
@@ -2037,7 +2037,7 @@ 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))
+                        }, valueRange = 0.5f..10f, colors = SliderDefaults.colors(thumbColor = MlPrimary, activeTrackColor = MlPrimary))
 
                         var walkKeepHold by remember { mutableStateOf(GreenZoneConstants.walkingKeepHoldMs / 1000f) }
                         Row(verticalAlignment = Alignment.CenterVertically) {