feat: Phase 4+5 — admin storage UI, backend proxy, CLAUDE.md enforcement

- backend/app/routers/storage_config.py: 5 admin-only endpoints proxying
  storage-service config + migration API (GET/PATCH/POST/DELETE)
- backend/app/main.py: register storage_config router
- frontend/src/api/client.ts: StorageStatus, MigrationStatus,
  StorageBackendConfig interfaces + 5 API functions
- frontend/src/pages/StorageAdminPage.tsx: full admin UI — backend health
  dot, driver selector (local/S3/WebDAV), conditional credential fields,
  Test & Migrate button, live 2s-poll migration progress bar, Cancel
- frontend/src/App.tsx: /admin/storage route (AdminRoute guard)
- CLAUDE.md: storage enforcement rule, updated Docker tables (6 services,
  3 volumes), §20 in merge checklist
- backend/CLAUDE.md, frontend/CLAUDE.md, doc-service/CLAUDE.md,
  ai-service/CLAUDE.md: updated to reflect storage-service integration
- tests/ALL_TESTS.md + tests/storage-service_tests.md: §20 (20 tests)
- backend/STATUS.md, frontend/STATUS.md: updated with new endpoints/routes
- changelog/2026-04-20_storage-service.md: full change log

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/main.py

@@ -9,6 +9,7 @@ from app.core.config import settings
 from app.database import AsyncSessionLocal
 from app.routers import admin, auth, categories_proxy, documents_proxy, groups, plugins, profile, services, users
 from app.routers import settings as settings_router
+from app.routers import storage_config
 from app.services.group_bootstrap import ensure_service_admin_groups
 from app.services.service_health import check_all, health_check_loop, register_services
 
@@ -52,6 +53,7 @@ app.include_router(admin.router, prefix="/api/admin", tags=["admin"])
 app.include_router(groups.router, prefix="/api/admin/groups", tags=["admin"])
 app.include_router(settings_router.router, prefix="/api/settings", tags=["settings"])
 app.include_router(services.router, prefix="/api/services", tags=["services"])
+app.include_router(storage_config.router, prefix="/api/admin", tags=["admin"])
 app.include_router(plugins.router, prefix="/api/plugins", tags=["plugins"])
 # categories_proxy MUST be registered before documents_proxy —
 # otherwise /api/documents/{path:path} swallows /api/documents/categories/*