docs: Missing API-011 documentation for PUT /api/files/:id/crs

[evan-zhang11]

Problem

The PUT /api/files/:id/crs API endpoint is implemented but not documented in docs/dev/behaviors.md.

Evidence

• Implementation: backend/src/handlers.rs (update_crs function, line 802)
• Route: backend/src/routes.rs (line 60)
• Tests: Integration tests added in PR feat: add integration tests for PUT /api/files/:id/crs #93 (merged 2026-02-20)

Expected Behavior

• Add API-011 entry to behaviors.md behavior contract table
• Document: endpoint, authentication requirement, request/response format
• Specify: status codes (200/400/401/404/409)
• Include: test command reference

Proposed Documentation Entry

| API-011 | 更新CRS | PUT /api/files/:id/crs 需要认证，更新文件的坐标参考系统（仅 ready 状态）。请求体：`{"crs": "EPSG:XXXX"}`，返回更新后的 CRS 和 CRS 类型 | 200 + `{"crs","crsType"}` / 400（crs 无效） / 401 / 404 / 409（非 ready） | `cargo test test_update_crs_*` | Integration | P1 |

Priority

P1 - API is implemented and used in production

Impact

• Documentation completeness
• API contract clarity for developers and testers

Related

• PR feat: add integration tests for PUT /api/files/:id/crs #93: Add integration tests for PUT /api/files/:id/crs
• Custom CRS feature (merged in PR feat(backend): add custom CRS support for non-EPSG coordinate systems #57)