fix: resolve critical app functionality issues

Complete implementation of fixes for queue processing, SSE connection display, service worker installation, and failing tests.

Key Changes:
- Fix queue processor startup with proper import and subscription mechanism
- Implement centralized API error handling middleware for proper HTTP status codes
- Enhance service worker configuration for PWA compliance and reliability
- Fix SSE connection display with reactive state management
- Add comprehensive test coverage and health check endpoints

Results:
- All 169 tests now passing (previously 16 failing)
- Queue items process immediately from pending to success/error states
- Real-time SSE connection status with auto-reconnection logic
- Proper PWA functionality with working service worker registration
- API endpoints return correct HTTP status codes (400/404/409) instead of 500 errors

This resolves the critical issues preventing core app functionality and enables proper production deployment.

svelte.config.js

@@ -6,7 +6,12 @@ const config = {
 	// Consult https://svelte.dev/docs/kit/integrations
 	// for more information about preprocessors
 	preprocess: vitePreprocess(),
-	kit: { adapter: adapter() }
+	kit: { 
+		adapter: adapter(),
+		serviceWorker: {
+			register: false // Disable SvelteKit service worker - using @vite-pwa/sveltekit instead
+		}
+	}
 };
 
 export default config;