Fix stuck processing jobs and increase timeouts

Background Job Processor:
- Add src/services/jobProcessor.ts that polls RunPod every 30s for stuck jobs
- Automatically completes or fails jobs that were abandoned (user navigated away)
- Times out jobs after 25 minutes

Client-Side Resume:
- Add GET /api/generate/pending endpoint to fetch user's processing jobs
- Add checkPendingJobs() that runs on login/page load
- Show notification banner when user has jobs generating in background
- Add "View Progress" button to resume polling for a job

Timeout Increases (10min → 25min):
- src/utils/validators.ts: request validation max/default
- src/config.ts: RUNPOD_MAX_TIMEOUT_MS default
- public/js/app.js: client-side polling maxTime
- src/services/jobProcessor.ts: background processor timeout

CI/CD Optimization:
- Add paths-ignore to backend build.yaml to skip rebuilds on frontend-only changes

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

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

frontend/src/index.ts

@@ -8,6 +8,7 @@ import { config } from './config.js';
 import { initDatabase, closeDatabase } from './db/index.js';
 import { createInitialAdmin } from './services/initService.js';
 import { SQLiteSessionStore } from './services/sessionService.js';
+import { startJobProcessor, stopJobProcessor } from './services/jobProcessor.js';
 import { apiRateLimiter } from './middleware/rateLimit.js';
 import { errorHandler } from './middleware/errorHandler.js';
 import { logger } from './utils/logger.js';
@@ -101,6 +102,9 @@ async function start() {
     // Create initial admin user if needed
     await createInitialAdmin();
 
+    // Start background job processor
+    startJobProcessor();
+
     // Start server
     const server = app.listen(config.port, () => {
       logger.info({ port: config.port, env: config.nodeEnv }, 'Server started');
@@ -112,6 +116,7 @@ async function start() {
 
       server.close(() => {
         logger.info('HTTP server closed');
+        stopJobProcessor();
         sessionStore.close();
         closeDatabase();
         logger.info('Database closed');