Add version display in admin sidebar footer

- Add /api/version endpoint that returns build info from env vars
- Add version footer to Layout.tsx showing build version, git SHA, and image tag
- Update Dockerfile to accept build args for version info (APP_BUILD_VERSION, APP_GIT_SHA, APP_BUILD_TIME, CONTAINER_IMAGE_TAG)

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

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

backend/src/index.ts

@@ -51,6 +51,7 @@ import apiPermissionsRoutes from './routes/api-permissions';
 import parallelScrapeRoutes from './routes/parallel-scrape';
 import scheduleRoutes from './routes/schedule';
 import crawlerSandboxRoutes from './routes/crawler-sandbox';
+import versionRoutes from './routes/version';
 import { trackApiUsage, checkRateLimit } from './middleware/apiTokenTracker';
 import { startCrawlScheduler } from './services/crawl-scheduler';
 import { validateWordPressPermissions } from './middleware/wordpressPermissions';
@@ -80,6 +81,7 @@ app.use('/api/api-permissions', apiPermissionsRoutes);
 app.use('/api/parallel-scrape', parallelScrapeRoutes);
 app.use('/api/schedule', scheduleRoutes);
 app.use('/api/crawler-sandbox', crawlerSandboxRoutes);
+app.use('/api/version', versionRoutes);
 
 async function startServer() {
   try {