Add real-time upgrade progress tracking via status file

- upgrade.sh now writes status to /data/coolify/source/.upgrade-status
- New /api/upgrade-status endpoint reads status file for real progress
- Frontend polls status API instead of simulating progress
- Falls back to health check when service goes down during restart

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

routes/api.php

@@ -19,10 +19,12 @@ use App\Models\Server;
 use Illuminate\Support\Facades\Route;
 
 Route::get('/health', [OtherController::class, 'healthcheck']);
+Route::get('/upgrade-status', [OtherController::class, 'upgradeStatus']);
 Route::group([
     'prefix' => 'v1',
 ], function () {
     Route::get('/health', [OtherController::class, 'healthcheck']);
+    Route::get('/upgrade-status', [OtherController::class, 'upgradeStatus']);
 });
 
 Route::post('/feedback', [OtherController::class, 'feedback']);