fix: implement persistent MongoDB connections and resolve race conditions

- Replace connect/disconnect pattern with persistent connection pool
- Add explicit database initialization on server startup
- Remove all dbDisconnect() calls from API endpoints to prevent race conditions
- Fix MongoNotConnectedError when scheduler runs concurrently with API requests
- Add connection pooling with proper MongoDB driver options
- Add safety check for recipes array in favorites utility

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

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

src/routes/api/rezepte/delete/+server.ts

@@ -1,6 +1,6 @@
 import type { RequestHandler } from '@sveltejs/kit';
 import { Recipe } from '../../../../models/Recipe';
-import { dbConnect, dbDisconnect } from '../../../../utils/db';
+import { dbConnect } from '../../../../utils/db';
 import type {RecipeModelType} from '../../../../types/types';
 import { error } from '@sveltejs/kit';
 // header: use for bearer token for now
@@ -14,7 +14,6 @@ export const POST: RequestHandler = async ({request, locals}) => {
   	const short_name = message.old_short_name
 	await dbConnect();
 	await Recipe.findOneAndDelete({short_name: short_name});
-  	await dbDisconnect();
 	return new Response(JSON.stringify({msg: "Deleted recipe successfully"}),{
 			    status: 200,
   	});