feat: database layer - PostgreSQL schema + memory fallback

- drizzle-orm + postgres dependencies
- Full schema: 12 tables covering all modules
- Graceful fallback: no DATABASE_URL → memory mode
- drizzle-kit config for migrations
- Memory store as generic CRUD layer
- dev.ts auto-initializes DB on startup

package-lock.json

@@ -11,7 +11,9 @@
         "@arco-design/web-react": "^2.66.0",
         "@hono/node-server": "^1.19.13",
         "@larksuiteoapi/node-sdk": "^1.60.0",
+        "drizzle-orm": "^0.45.2",
         "hono": "^4.7.0",
+        "postgres": "^3.4.9",
         "react": "^18.3.0",
         "react-dom": "^18.3.0"
       },
@@ -2577,6 +2579,131 @@
         "csstype": "^3.0.2"
       }
     },
+    "node_modules/drizzle-orm": {
+      "version": "0.45.2",
+      "resolved": "https://registry.npmmirror.com/drizzle-orm/-/drizzle-orm-0.45.2.tgz",
+      "integrity": "sha512-kY0BSaTNYWnoDMVoyY8uxmyHjpJW1geOmBMdSSicKo9CIIWkSxMIj2rkeSR51b8KAPB7m+qysjuHme5nKP+E5Q==",
+      "license": "Apache-2.0",
+      "peerDependencies": {
+        "@aws-sdk/client-rds-data": ">=3",
+        "@cloudflare/workers-types": ">=4",
+        "@electric-sql/pglite": ">=0.2.0",
+        "@libsql/client": ">=0.10.0",
+        "@libsql/client-wasm": ">=0.10.0",
+        "@neondatabase/serverless": ">=0.10.0",
+        "@op-engineering/op-sqlite": ">=2",
+        "@opentelemetry/api": "^1.4.1",
+        "@planetscale/database": ">=1.13",
+        "@prisma/client": "*",
+        "@tidbcloud/serverless": "*",
+        "@types/better-sqlite3": "*",
+        "@types/pg": "*",
+        "@types/sql.js": "*",
+        "@upstash/redis": ">=1.34.7",
+        "@vercel/postgres": ">=0.8.0",
+        "@xata.io/client": "*",
+        "better-sqlite3": ">=7",
+        "bun-types": "*",
+        "expo-sqlite": ">=14.0.0",
+        "gel": ">=2",
+        "knex": "*",
+        "kysely": "*",
+        "mysql2": ">=2",
+        "pg": ">=8",
+        "postgres": ">=3",
+        "sql.js": ">=1",
+        "sqlite3": ">=5"
+      },
+      "peerDependenciesMeta": {
+        "@aws-sdk/client-rds-data": {
+          "optional": true
+        },
+        "@cloudflare/workers-types": {
+          "optional": true
+        },
+        "@electric-sql/pglite": {
+          "optional": true
+        },
+        "@libsql/client": {
+          "optional": true
+        },
+        "@libsql/client-wasm": {
+          "optional": true
+        },
+        "@neondatabase/serverless": {
+          "optional": true
+        },
+        "@op-engineering/op-sqlite": {
+          "optional": true
+        },
+        "@opentelemetry/api": {
+          "optional": true
+        },
+        "@planetscale/database": {
+          "optional": true
+        },
+        "@prisma/client": {
+          "optional": true
+        },
+        "@tidbcloud/serverless": {
+          "optional": true
+        },
+        "@types/better-sqlite3": {
+          "optional": true
+        },
+        "@types/pg": {
+          "optional": true
+        },
+        "@types/sql.js": {
+          "optional": true
+        },
+        "@upstash/redis": {
+          "optional": true
+        },
+        "@vercel/postgres": {
+          "optional": true
+        },
+        "@xata.io/client": {
+          "optional": true
+        },
+        "better-sqlite3": {
+          "optional": true
+        },
+        "bun-types": {
+          "optional": true
+        },
+        "expo-sqlite": {
+          "optional": true
+        },
+        "gel": {
+          "optional": true
+        },
+        "knex": {
+          "optional": true
+        },
+        "kysely": {
+          "optional": true
+        },
+        "mysql2": {
+          "optional": true
+        },
+        "pg": {
+          "optional": true
+        },
+        "postgres": {
+          "optional": true
+        },
+        "prisma": {
+          "optional": true
+        },
+        "sql.js": {
+          "optional": true
+        },
+        "sqlite3": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/dunder-proto": {
       "version": "1.0.1",
       "resolved": "https://registry.npmmirror.com/dunder-proto/-/dunder-proto-1.0.1.tgz",
@@ -3811,6 +3938,19 @@
         "node": "^10 || ^12 || >=14"
       }
     },
+    "node_modules/postgres": {
+      "version": "3.4.9",
+      "resolved": "https://registry.npmmirror.com/postgres/-/postgres-3.4.9.tgz",
+      "integrity": "sha512-GD3qdB0x1z9xgFI6cdRD6xu2Sp2WCOEoe3mtnyB5Ee0XrrL5Pe+e4CCnJrRMnL1zYtRDZmQQVbvOttLnKDLnaw==",
+      "license": "Unlicense",
+      "engines": {
+        "node": ">=12"
+      },
+      "funding": {
+        "type": "individual",
+        "url": "https://github.com/sponsors/porsager"
+      }
+    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "resolved": "https://registry.npmmirror.com/prelude-ls/-/prelude-ls-1.2.1.tgz",