feat(ProcessManager): add Bun availability check and improve PID file validation

- Implemented a method to check if Bun is available in the system PATH.
- Updated the startWithBun method to return an error if Bun is not found.
- Enhanced PID file parsing to validate required fields and their types.
- Cleaned up stale PID files if the process is no longer alive.

fix(SettingsRoutes): clear port cache after updating settings

- Added a call to clearPortCache after writing updated settings to ensure the application uses the latest configuration.

src/services/worker/http/routes/SettingsRoutes.ts

@@ -21,6 +21,7 @@ import {
 } from '../../../../constants/observation-metadata.js';
 import { BaseRouteHandler } from '../BaseRouteHandler.js';
 import { SettingsDefaultsManager } from '../../../../shared/SettingsDefaultsManager.js';
+import { clearPortCache } from '../../../../shared/worker-utils.js';
 
 export class SettingsRoutes extends BaseRouteHandler {
   constructor(
@@ -162,6 +163,9 @@ export class SettingsRoutes extends BaseRouteHandler {
     // Write back
     writeFileSync(settingsPath, JSON.stringify(settings, null, 2), 'utf-8');
 
+    // Clear port cache to force re-reading from updated settings
+    clearPortCache();
+
     logger.info('WORKER', 'Settings updated');
     res.json({ success: true, message: 'Settings updated successfully' });
   });