[AI] Fix API build output path (dist/index.js instead of dist/api/index.js) (#7084)

* [AI] Fix API build output path (dist/index.js instead of dist/api/index.js)

- Set rootDir in packages/api/tsconfig.json so output is under dist/ not dist/api/
- Remove loot-core pegjs.ts from include; add local typings/pegjs.d.ts
- Use mkdir -p in build:migrations for idempotent build
- Exclude **/@types/** so declaration output does not conflict with input

Made-with: Cursor

* Update TypeScript configuration in api package to refine exclude patterns

packages/api/tsconfig.json

@@ -9,12 +9,13 @@
     "noEmit": false,
     "declaration": true,
     "outDir": "dist",
+    "rootDir": ".",
     "declarationDir": "@types",
     "paths": {
       "loot-core/*": ["./@types/loot-core/src/*"]
     },
     "plugins": [{ "name": "typescript-strict-plugin", "paths": ["."] }]
   },
-  "include": [".", "../../packages/loot-core/typings/pegjs.ts"],
+  "include": ["."],
   "exclude": ["**/node_modules/*", "dist", "@types", "*.test.ts"]
 }