feat: automatic worker restart on version updates

Critical improvement for seamless upgrades across all versions.

Changes:
1. Added /api/version endpoint to worker service
   - Returns current worker version from package.json

2. Added version checking in worker-utils.ts
   - getPluginVersion() - reads plugin's package.json version
   - getWorkerVersion() - fetches version from worker API
   - ensureWorkerVersionMatches() - compares and restarts if needed

3. Modified ensureWorkerRunning()
   - Now calls ensureWorkerVersionMatches() after health check
   - Automatically restarts worker when version mismatch detected
   - Logs version mismatch for debugging

Impact:
- Users no longer need to manually restart worker after upgrades
- Eliminates connection errors from running old worker code
- Critical for v7.1.1 (Bun auto-install) and all future releases
- Fixes the issue where PR #236 changes weren't applied until manual restart

Testing:
- Version endpoint working: returns {"version":"7.1.0"}
- Worker health check: passing
- Auto-restart logic: triggers on version mismatch

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

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

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