feat: persist notification preferences to server-side settings

Notification prefs are now included in the PUT /api/settings payload
and stored in ~/.claudeman/settings.json. On page load, server-stored
prefs are loaded as fallback when localStorage is empty (e.g. new
browser or cleared cache).

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

src/web/server.ts

@@ -1306,7 +1306,7 @@ export class WebServer extends EventEmitter {
     });
 
     this.app.put('/api/settings', async (req) => {
-      const settings = req.body as { defaultClaudeMdPath?: string; defaultWorkingDir?: string };
+      const settings = req.body as Record<string, unknown>;
 
       try {
         const dir = dirname(settingsPath);