fix: migrate to Prisma 7 driver adapter (libsql) for SQLite

Prisma 7 removed support for `url` in schema.prisma datasources and the
`engineType = "library"` native binary engine. All connections now go
through a driver adapter.

- Remove engineType and url from schema.prisma (no longer supported)
- Configure prisma.config.ts with migrate.adapter using @libsql/client
- Instantiate PrismaClient with PrismaLibSQL adapter in src/lib/prisma.ts
- Add @libsql/client and @prisma/adapter-libsql dependencies
- Remove PRISMA_CLIENT_ENGINE_TYPE from Dockerfile (obsolete)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/prisma.ts

@@ -1,4 +1,6 @@
 import { PrismaClient } from '@prisma/client'
+import { PrismaLibSQL } from '@prisma/adapter-libsql'
+import { createClient } from '@libsql/client'
 
 const globalForPrisma = globalThis as unknown as {
   prisma: PrismaClient | undefined
@@ -6,7 +8,12 @@ const globalForPrisma = globalThis as unknown as {
 
 function getPrismaClient(): PrismaClient {
   if (!globalForPrisma.prisma) {
+    const libsql = createClient({
+      url: process.env.DATABASE_URL ?? 'file:./dev.db',
+    })
+    const adapter = new PrismaLibSQL(libsql)
     globalForPrisma.prisma = new PrismaClient({
+      adapter,
       log: process.env.NODE_ENV === 'development' ? ['query', 'error', 'warn'] : ['error'],
     })
   }
@@ -15,8 +22,6 @@ function getPrismaClient(): PrismaClient {
 
 // Use a Proxy so `new PrismaClient()` is only called when a property
 // is first accessed (inside a request handler), NOT at module import time.
-// This prevents PrismaClientConstructorValidationError during Next.js
-// static analysis / "Collecting page data" phase.
 export const prisma = new Proxy({} as PrismaClient, {
   get(_target, prop) {
     return Reflect.get(getPrismaClient(), prop)