完善分层 AGENTS.md，便于快速定位代码

springboot-backend/src/main/java/com/admin/AGENTS.md

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+# SPRINGBOOT BACKEND (com.admin) KNOWLEDGE BASE
+
+## OVERVIEW
+Primary Java code for the admin API. Controllers expose `/api/v1/*` endpoints and return `R` response envelopes.
+
+## STRUCTURE
+```
+springboot-backend/src/main/java/com/admin/
+├── controller/  # REST controllers (e.g., /api/v1/user)
+├── service/     # Business logic interfaces + impl/
+├── mapper/      # MyBatis Plus mappers
+├── entity/      # DB entities
+├── config/      # WebMvc/JWT/CORS/WebSocket config
+└── common/      # DTOs, auth, exception handling, utilities
+```
+
+## WHERE TO LOOK
+| Task | Location | Notes |
+|------|----------|-------|
+| User/login endpoints | `springboot-backend/src/main/java/com/admin/controller/UserController.java` | `/api/v1/user/*` |
+| Auth enforcement | `springboot-backend/src/main/java/com/admin/config/WebMvcConfig.java` | Intercepts `/api/**`, excludes login/config/captcha |
+| JWT validation | `springboot-backend/src/main/java/com/admin/common/interceptor/JwtInterceptor.java` | Requires `Authorization` header |
+| Admin-only ops | `springboot-backend/src/main/java/com/admin/common/annotation/RequireRole.java` | Enforced by `RoleAspect` |
+| Response envelope | `springboot-backend/src/main/java/com/admin/common/lang/R.java` | `code == 0` success |
+| Global error handling | `springboot-backend/src/main/java/com/admin/common/exception/GlobalExceptionHandler.java` | Maps exceptions -> `R.err(...)` |
+
+## CONVENTIONS
+- Controllers are mostly `@PostMapping` (even for list/get/delete) and use `/api/v1/*` prefixes.
+- JWT is custom (no 3p lib) and includes `role_id` in payload (`springboot-backend/src/main/java/com/admin/common/utils/JwtUtil.java`).
+
+## ANTI-PATTERNS
+- Do not change auth header format lightly: frontend expects `Authorization: <token>` (no `Bearer`).