chore(db): migrate from SQLite to PostgreSQL

- Change Prisma provider from sqlite to postgresql
- Replace better-sqlite3 adapter with @prisma/adapter-pg
- Update prisma.config.ts and lib/prisma.ts for PostgreSQL
- Add DATABASE_URL to .env.local
- Regenerate Prisma client for PostgreSQL
- Recreate migrations for PostgreSQL database

lib/prisma.ts

@@ -1,11 +1,12 @@
-import Database from "better-sqlite3";
-import { PrismaBetterSqlite3 } from "@prisma/adapter-better-sqlite3";
+import { Pool } from "pg";
+import { PrismaPg } from "@prisma/adapter-pg";
 import { PrismaClient } from "./generated/prisma/client";
 
 const globalForPrisma = globalThis as unknown as { prisma?: PrismaClient };
 
 function createPrisma() {
-  const adapter = new PrismaBetterSqlite3({ url: "./wikirush.db" });
+  const pool = new Pool({ connectionString: process.env.DATABASE_URL });
+  const adapter = new PrismaPg(pool);
   return new PrismaClient({ adapter });
 }