fix: Prisma 7 adapter-based connection (no url in schema)

- Use @prisma/adapter-pg for PrismaClient (Prisma 7 removed datasourceUrl/datasources)
- prisma.config.ts: migrate.url for CLI commands
- schema.prisma: no url in datasource (Prisma 7 requirement)

src/lib/prisma.ts

@@ -1,9 +1,15 @@
 import { PrismaClient } from "@prisma/client";
+import { PrismaPg } from "@prisma/adapter-pg";
 
 const globalForPrisma = globalThis as unknown as {
   prisma: PrismaClient | undefined;
 };
 
-export const prisma = globalForPrisma.prisma ?? new PrismaClient();
+function createPrismaClient() {
+  const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL! });
+  return new PrismaClient({ adapter });
+}
+
+export const prisma = globalForPrisma.prisma ?? createPrismaClient();
 
 if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;