refactor: 降级 Drizzle ORM 至 0.45.x 稳定版，对齐 Better Auth 兼容性

- drizzle-orm 1.0.0-beta.15 → 0.45.2, drizzle-kit → 0.31.10
- RQBv2 defineRelations() → 旧版 relations() 回调语法
- drizzle-orm/zod → drizzle-zod 独立包
- auth/schema.ts 改由 Better Auth CLI 生成（bun run db:auth）
- db/schema/index.ts 选择性导出表（不导出生成文件中的旧版 relations）
- 删除 db:push script，强制 db:generate → db:migrate 工作流
- 重建迁移基线（删除旧迁移目录，全新生成初始迁移）

AGENTS.md

@@ -42,6 +42,7 @@ bun run fix              # Lint + format (Biome auto-fix)
 bun run typecheck        # TypeScript check across monorepo
 
 # Database (in apps/server) — ALWAYS use migration workflow, never db:push
+bun run db:auth          # Regenerate Better Auth schema (after upgrading better-auth)
 bun run db:generate      # Generate migrations from schema changes
 bun run db:migrate       # Run pending migrations
 bun run db:studio        # Open Drizzle Studio
@@ -88,13 +89,15 @@ Biome auto-organizes. Order: 1) External packages → 2) Internal `@/*` aliases
 - ORPC: Use `ORPCError` with proper codes (`NOT_FOUND`, `UNAUTHORIZED`, `INTERNAL_SERVER_ERROR`)
 - Never use empty catch blocks
 
-## Database (Drizzle ORM v1 beta + postgres-js)
+## Database (Drizzle ORM + postgres-js)
 
-- **ORM**: Drizzle ORM `1.0.0-beta` (RQBv2)
+- **ORM**: Drizzle ORM `0.45.x` (stable)
 - **Driver**: `drizzle-orm/postgres-js` (NOT `bun-sql`)
-- **Validation**: `drizzle-orm/zod` (built-in, NOT separate `drizzle-zod` package)
-- **Relations**: Defined via `defineRelations()` — RQBv2 object syntax
-- **Query style**: `db.query.tableName.findMany({ orderBy: { createdAt: 'desc' }, where: { id: 1 } })`
+- **Validation**: `drizzle-zod` (separate package, NOT `drizzle-orm/zod`)
+- **Relations**: Defined via `relations()` from `drizzle-orm` — callback syntax
+- **Query style**: `db.query.tableName.findMany({ where: (t, { eq }) => eq(t.col, val), orderBy: (t, { asc }) => asc(t.col) })`
+- **Auth schema**: Generated by Better Auth CLI (`bun run db:auth`), **never hand-edit**
+- **Schema re-export**: `db/schema/index.ts` selectively exports tables only (not relations) from auth schema
 - **Migration workflow**: Always `db:generate` → `db:migrate`. **Never** use `db:push`.
 
 ## Environment Variables