fix(signaling): call startForeground() first in onCreate() to reduce FGS timeout risk

[SERDUN]

Problem

SignalingForegroundService.onCreate() called startForeground() as the 5th operation, after a blocking SharedPreferences read (StorageDelegate.getCallbackDispatcher()).

Under Xiaomi HyperOS memory pressure, that SharedPrefs IPC blocks the main thread for 50–500ms. Combined with the main thread being busy during Flutter cold start, the total delay from startForegroundService() to startForeground() exceeded Xiaomi's aggressive ~1.2s window (vs the standard 10s), causing ForegroundServiceDidNotStartInTimeException.

From the crash log:

T+0.000s  startForegroundService()
T+1.205s  Xiaomi removes ServiceRecord
T+2.252s  startForeground() → rejected → crash

Fix

Move startForeground() to be the first call after super.onCreate(), before any IPC.

// Before
override fun onCreate() {
    super.onCreate()
    Log.d(TAG, ...)
    instance = this
    val callbackHandle = StorageDelegate.getCallbackDispatcher(applicationContext)  // SharedPrefs IPC
    flutterEngineHelper = FlutterEngineHelper(...)
    startForeground()  // 5th — too late under pressure
    isRunning = true
}

// After
override fun onCreate() {
    super.onCreate()
    startForeground()  // first — no IPC before it

    Log.d(TAG, ...)
    instance = this
    val callbackHandle = StorageDelegate.getCallbackDispatcher(applicationContext)
    flutterEngineHelper = FlutterEngineHelper(...)
    isRunning = true
}

Safety

• startForeground() has no dependency on flutterEngineHelper or callbackHandle — the engine starts in onStartCommand(), which runs after onCreate() completes
• instance is only read by WebtritSignalingServicePlugin.notifyIsolateReady(), which is called after onStartCommand() + Dart isolate ready — well after onCreate() completes
• isRunning placement at the end of onCreate() is unchanged in meaning

Part of

Umbrella: #1099

[Copilot]

Pull request overview

Moves startForeground() to the first operation in SignalingForegroundService.onCreate() (immediately after super.onCreate()) to minimize the risk of OEM-specific foreground-service start timeouts caused by blocking IPC during service initialization.

Changes:

• Call startForeground() at the beginning of onCreate() (before the SharedPreferences read for the callback handle).
• Keep the rest of initialization order intact (logging, instance, FlutterEngineHelper, isRunning).