migrate: replace pg with Prisma ORM

- Add prisma/schema.prisma with Project/Task models, enums, and relations
- Create src/lib/db.ts singleton Prisma client
- Refactor all 5 API routes to use Prisma queries
- Replace migrate.ts with seed.ts for initial data
- Update Dockerfile for Prisma lifecycle (copy generated client)
- Update tsconfig.json with @/generated/* path alias
- Remove pg and @types/pg dependencies
- Add prisma.config.ts for Prisma 6 config
- Update .gitignore for generated Prisma client

package.json

@@ -6,24 +6,28 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "db:generate": "prisma generate",
+    "db:migrate": "prisma migrate deploy",
+    "db:seed": "tsx src/server/db/seed.ts"
   },
   "dependencies": {
+    "@prisma/client": "^6.19.3",
     "date-fns": "^4.1.0",
     "next": "16.2.4",
-    "pg": "^8.20.0",
+    "prisma": "^6.19.3",
     "react": "19.2.4",
     "react-dom": "19.2.4"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
     "@types/node": "^20",
-    "@types/pg": "^8.20.0",
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "eslint": "^9",
     "eslint-config-next": "16.2.4",
     "tailwindcss": "^4",
+    "tsx": "^4.19.0",
     "typescript": "^5"
   }
 }