chore: isolate frontend and backend via npm workspaces and @mmapp/contracts

Co-authored-by: Cursor <cursoragent@cursor.com>

tsconfig.json

@@ -30,5 +30,5 @@
     ".next/dev/types/**/*.ts",
     "**/*.mts"
   ],
-  "exclude": ["node_modules"]
+  "exclude": ["node_modules", "backend", "packages"]
 }