chore: ZXDB env validation, MySQL setup, API & UI

This sanity commit wires up the initial ZXDB integration and a minimal UI to explore it.

Key changes:
- Add Zod-based env parsing (`src/env.ts`) validating `ZXDB_URL` as a mysql:// URL (t3.gg style).
- Configure Drizzle ORM with mysql2 connection pool (`src/server/db.ts`) driven by `ZXDB_URL`.
- Define minimal ZXDB schema models (`src/server/schema/zxdb.ts`): `entries` and helper `search_by_titles`.
- Implement repository search with pagination using helper table (`src/server/repo/zxdb.ts`).
- Expose Next.js API route `GET /api/zxdb/search` with Zod query validation and Node runtime (`src/app/api/zxdb/search/route.ts`).
- Create new app section “ZXDB Explorer” at `/zxdb` with search UI, results table, and pagination (`src/app/zxdb/*`).
- Add navbar link to ZXDB (`src/components/Navbar.tsx`).
- Update example.env with readonly-role notes and example `ZXDB_URL`.
- Add drizzle-kit config scaffold (`drizzle.config.ts`).
- Update package.json deps: drizzle-orm, mysql2, zod; devDeps: drizzle-kit. Lockfile updated.
- Extend .gitignore to exclude large ZXDB structure dump.

Notes:
- Ensure ZXDB data and helper tables are loaded (see `ZXDB/scripts/ZXDB_help_search.sql`).
- This commit provides structure-only browsing; future work can enrich schema (authors, labels, publishers) and UI filters.

Signed-off-by: Junie@lucy.xalior.com

package.json

@@ -17,7 +17,10 @@
     "react-bootstrap": "^2.10.10",
     "react-bootstrap-icons": "^1.11.6",
     "react-dom": "19.1.0",
-    "typescript": "^5.9.3"
+    "typescript": "^5.9.3",
+    "drizzle-orm": "^0.36.1",
+    "mysql2": "^3.12.0",
+    "zod": "^3.23.8"
   },
   "devDependencies": {
     "@eslint/eslintrc": "^3.3.3",
@@ -26,6 +29,7 @@
     "@types/react-dom": "^19.2.3",
     "eslint": "^9.39.1",
     "eslint-config-next": "15.5.4",
-    "sass": "^1.94.2"
+    "sass": "^1.94.2",
+    "drizzle-kit": "^0.30.1"
   }
 }