feat: auto-detect device preset from BLE name

VBT260400xy → FLAT, VBT260402xy → NEW_CASE2, VBT260403xy → NEW_CASE1
2025MEDIP → LEGACY_5CH

Auto-called on BLE connect. Logged to debug.

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

app/src/main/java/com/example/medilightv2android/ble/BleManager.kt

@@ -374,6 +374,9 @@ class BleManager private constructor(private val context: Context) {
                         if (idx >= 0) discoveredDevices[idx] = discoveredDevices[idx].copy(isConnected = true, isConnecting = false)
                         isConnected.value = true
                         connectedDeviceName.value = try { gatt.device.name ?: "Unknown" } catch (_: Exception) { "Unknown" }
+                        // Auto-detect device preset from name
+                        com.example.medilightv2android.managers.PiezoHW.autoDetectPreset(connectedDeviceName.value)
+                        logd { "Device preset: ${com.example.medilightv2android.managers.PiezoHW.presetName} (from '${connectedDeviceName.value}')" }
 
                         // Save last connected device address
                         try {

app/src/main/java/com/example/medilightv2android/managers/PiezoBVEstimator.kt

@@ -37,8 +37,24 @@ object PiezoHW {
         NEW_CASE2
     }
 
-    /** ★ 여기만 바꾸면 전체 적용 ★ */
-    val activePreset: DevicePreset = DevicePreset.FLAT
+    /** 현재 활성 preset — 기기 연결 시 자동 감지, 수동 변경도 가능 */
+    var activePreset: DevicePreset = DevicePreset.FLAT
+
+    /**
+     * BLE 기기 이름으로 preset 자동 감지.
+     * VBT26040x0y: x=0 → FLAT, x=2 → NEW_CASE2, x=3 → NEW_CASE1
+     */
+    fun autoDetectPreset(deviceName: String) {
+        if (deviceName.startsWith("VBT2604") && deviceName.length >= 9) {
+            when (deviceName[7]) {
+                '0' -> activePreset = DevicePreset.FLAT
+                '2' -> activePreset = DevicePreset.NEW_CASE2
+                '3' -> activePreset = DevicePreset.NEW_CASE1
+            }
+        } else if (deviceName.startsWith("2025MEDIP")) {
+            activePreset = DevicePreset.LEGACY_5CH
+        }
+    }
 
     // BV용 수직 채널 (CH0~CH3)
     val sensorZMm: DoubleArray