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>

Dockerfile

@@ -17,7 +17,6 @@ COPY . .
 
 # Generate Prisma Client (with SQLite)
 ENV DATABASE_URL="file:/app/data/dev.db"
-ENV PRISMA_CLIENT_ENGINE_TYPE=library
 RUN npx prisma generate
 
 # Disable telemetry during build
@@ -32,7 +31,6 @@ WORKDIR /app
 ENV NODE_ENV=production
 ENV NEXT_TELEMETRY_DISABLED=1
 ENV DATABASE_URL="file:/app/data/dev.db"
-ENV PRISMA_CLIENT_ENGINE_TYPE=library
 
 RUN addgroup --system --gid 1001 nodejs
 RUN adduser --system --uid 1001 nextjs