Custom RTMP saved accounts, RTMP test server, composition pipeline

- Backend: POST /providers/accounts/custom-rtmp to save reusable RTMP servers
- Backend: Encrypt rtmpUrl/streamKey in existing token fields, decrypt on GET
- Backend: Skip token revocation on DELETE for CUSTOM_RTMP accounts
- Backend: Decrypt CUSTOM_RTMP credentials into destinations on plan create/update
- Android: Add rtmpUrl/streamKey to LinkedAccount entity + shared parcelable (Room v6)
- Android: Add Custom RTMP dialog in AccountsScreen, auto-fill in plan destination picker
- Android: Handle CUSTOM_RTMP accounts in CreatePlanViewModel.loadExistingPlan
- Add local RTMP test server (tools/rtmp-server.js) with auto-ffplay on publish
- Add composition pipeline native code

app/src/main/java/com/omixlab/lckcontrol/streaming/NativeStreamingEngine.kt

@@ -2,6 +2,7 @@ package com.omixlab.lckcontrol.streaming
 
 import android.hardware.HardwareBuffer
 import android.util.Log
+import android.view.Surface
 
 /**
  * Thin JNI wrapper around the C++ StreamingEngine.
@@ -77,6 +78,52 @@ class NativeStreamingEngine {
         return nativeIsRunning(nativePtr)
     }
 
+    // Preview surface
+    fun setPreviewSurface(surface: Surface) {
+        if (nativePtr == 0L) return
+        nativeSetPreviewSurface(nativePtr, surface)
+    }
+
+    fun removePreviewSurface() {
+        if (nativePtr == 0L) return
+        nativeRemovePreviewSurface(nativePtr)
+    }
+
+    // Composition layers
+    fun addCompositionLayer(
+        rgbaData: ByteArray, w: Int, h: Int,
+        posX: Float, posY: Float, scaleX: Float, scaleY: Float,
+        rotation: Float, opacity: Float, zOrder: Int, tag: String,
+    ): Int {
+        if (nativePtr == 0L) return -1
+        return nativeAddCompositionLayer(nativePtr, rgbaData, w, h,
+            posX, posY, scaleX, scaleY, rotation, opacity, zOrder, tag)
+    }
+
+    fun removeCompositionLayer(layerId: Int) {
+        if (nativePtr == 0L) return
+        nativeRemoveCompositionLayer(nativePtr, layerId)
+    }
+
+    fun updateCompositionLayerTransform(
+        layerId: Int, posX: Float, posY: Float,
+        scaleX: Float, scaleY: Float, rotation: Float,
+    ) {
+        if (nativePtr == 0L) return
+        nativeUpdateCompositionLayerTransform(nativePtr, layerId,
+            posX, posY, scaleX, scaleY, rotation)
+    }
+
+    fun updateCompositionLayerOpacity(layerId: Int, opacity: Float) {
+        if (nativePtr == 0L) return
+        nativeUpdateCompositionLayerOpacity(nativePtr, layerId, opacity)
+    }
+
+    fun setCompositionLayerEnabled(layerId: Int, enabled: Boolean) {
+        if (nativePtr == 0L) return
+        nativeSetCompositionLayerEnabled(nativePtr, layerId, enabled)
+    }
+
     // Called from native code (JNI callbacks)
     @Suppress("unused")
     private fun onNativeStats(videoBitrate: Long, audioBitrate: Long, fps: Int, droppedFrames: Int) {
@@ -109,4 +156,22 @@ class NativeStreamingEngine {
     private external fun nativeStop(ptr: Long)
     private external fun nativeDestroy(ptr: Long)
     private external fun nativeIsRunning(ptr: Long): Boolean
+
+    // Preview surface
+    private external fun nativeSetPreviewSurface(ptr: Long, surface: Surface)
+    private external fun nativeRemovePreviewSurface(ptr: Long)
+
+    // Composition layers
+    private external fun nativeAddCompositionLayer(
+        ptr: Long, rgbaData: ByteArray, w: Int, h: Int,
+        posX: Float, posY: Float, scaleX: Float, scaleY: Float,
+        rotation: Float, opacity: Float, zOrder: Int, tag: String,
+    ): Int
+    private external fun nativeRemoveCompositionLayer(ptr: Long, layerId: Int)
+    private external fun nativeUpdateCompositionLayerTransform(
+        ptr: Long, layerId: Int, posX: Float, posY: Float,
+        scaleX: Float, scaleY: Float, rotation: Float,
+    )
+    private external fun nativeUpdateCompositionLayerOpacity(ptr: Long, layerId: Int, opacity: Float)
+    private external fun nativeSetCompositionLayerEnabled(ptr: Long, layerId: Int, enabled: Boolean)
 }

app/src/main/java/com/omixlab/lckcontrol/streaming/StreamingManager.kt

@@ -1,12 +1,15 @@
 package com.omixlab.lckcontrol.streaming
 
+import android.graphics.Bitmap
 import android.hardware.HardwareBuffer
 import android.util.Log
+import android.view.Surface
 import com.omixlab.lckcontrol.shared.StreamPlan
 import com.omixlab.lckcontrol.shared.StreamingConfig
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import java.nio.ByteBuffer
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -153,4 +156,61 @@ class StreamingManager @Inject constructor() {
     }
 
     fun isStreaming(): Boolean = _state.value == StreamingState.LIVE
+
+    // --- Preview surface ---
+
+    fun setPreviewSurface(surface: Surface) {
+        engine?.setPreviewSurface(surface)
+    }
+
+    fun removePreviewSurface() {
+        engine?.removePreviewSurface()
+    }
+
+    // --- Composition layers ---
+
+    fun addCompositionLayer(
+        bitmap: Bitmap,
+        posX: Float, posY: Float,
+        scaleX: Float, scaleY: Float,
+        rotation: Float, opacity: Float,
+        zOrder: Int, tag: String,
+    ): Int {
+        val rgba = bitmapToRgba(bitmap)
+        return engine?.addCompositionLayer(
+            rgba, bitmap.width, bitmap.height,
+            posX, posY, scaleX, scaleY, rotation, opacity, zOrder, tag,
+        ) ?: -1
+    }
+
+    fun removeCompositionLayer(layerId: Int) {
+        engine?.removeCompositionLayer(layerId)
+    }
+
+    fun updateCompositionLayerTransform(
+        layerId: Int, posX: Float, posY: Float,
+        scaleX: Float, scaleY: Float, rotation: Float,
+    ) {
+        engine?.updateCompositionLayerTransform(layerId, posX, posY, scaleX, scaleY, rotation)
+    }
+
+    fun updateCompositionLayerOpacity(layerId: Int, opacity: Float) {
+        engine?.updateCompositionLayerOpacity(layerId, opacity)
+    }
+
+    fun setCompositionLayerEnabled(layerId: Int, enabled: Boolean) {
+        engine?.setCompositionLayerEnabled(layerId, enabled)
+    }
+
+    private fun bitmapToRgba(bitmap: Bitmap): ByteArray {
+        val argbBitmap = if (bitmap.config != Bitmap.Config.ARGB_8888) {
+            bitmap.copy(Bitmap.Config.ARGB_8888, false)
+        } else {
+            bitmap
+        }
+        val buffer = ByteBuffer.allocate(argbBitmap.byteCount)
+        argbBitmap.copyPixelsToBuffer(buffer)
+        if (argbBitmap !== bitmap) argbBitmap.recycle()
+        return buffer.array()
+    }
 }