Upgrade to Prisma 7 with adapter pattern

- Update prisma and @prisma/client to ^7.0.0
- Add @prisma/adapter-pg for PostgreSQL connections
- Create prisma.config.ts for datasource configuration
- Remove url from schema.prisma datasource block
- Update prisma.ts to use PrismaPg adapter pattern

Breaking change in Prisma 7: datasource url now configured
via prisma.config.ts instead of schema.prisma

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

prisma/prisma.config.ts

@@ -0,0 +1,12 @@
+import 'dotenv/config'
+import { defineConfig, env } from 'prisma/config'
+
+export default defineConfig({
+  schema: 'prisma/schema.prisma',
+  migrations: {
+    path: 'prisma/migrations',
+  },
+  datasource: {
+    url: env('DATABASE_URL'),
+  },
+})

prisma/schema.prisma

@@ -7,7 +7,7 @@ generator client {
 
 datasource db {
   provider = "postgresql"
-  url      = env("DATABASE_URL")
+  // url configured in prisma.config.ts (Prisma 7+)
 }
 
 // ============================================================================