Scaffold Next.js 16 app + wire NextAuth Credentials to auth core

Minimal but real App Router app that builds (next build exit 0):
- src/lib/auth.ts: NextAuth v5 Credentials provider calling checkLogin()
  (argon2id/bcrypt + md5->argon2id upgrade gated by CONVERT_PASSWORDS), JWT
  session, /api/auth/[...nextauth] route handler.
- src/app: root layout, home (force-dynamic, reads hotel_name via siteSettings),
  /login client form (signIn).
- next.config.ts: pinned turbopack.root, serverExternalPackages for the Prisma
  MariaDB adapter; tsconfig set up for Next.

Routes: / (dynamic), /login, /api/auth. Verified: next build exit 0, 28 tests.
Still needs DB+APP_KEY to run auth end-to-end. i18n/middleware/pages to follow.

tsconfig.json

@@ -1,20 +1,42 @@
 {
   "compilerOptions": {
     "target": "ES2022",
-    "lib": ["ES2022"],
-    "module": "ESNext",
-    "moduleResolution": "Bundler",
+    "lib": [
+      "dom",
+      "dom.iterable",
+      "esnext"
+    ],
+    "allowJs": true,
+    "skipLibCheck": true,
     "strict": true,
-    "noUncheckedIndexedAccess": true,
     "noEmit": true,
     "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
     "resolveJsonModule": true,
     "isolatedModules": true,
-    "skipLibCheck": true,
-    "types": ["node"],
+    "jsx": "react-jsx",
+    "incremental": true,
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
     "baseUrl": ".",
-    "paths": { "@/*": ["./src/*"] }
+    "paths": {
+      "@/*": [
+        "./src/*"
+      ]
+    }
   },
-  "include": ["src", "scripts", "prisma.config.ts", "vitest.config.ts"],
-  "exclude": ["node_modules"]
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts"
+  ],
+  "exclude": [
+    "node_modules"
+  ]
 }