chore: remove unauthenticated dead-code GET /api/v1/retrieval/ status endpoint (#24497)

The `get_status()` handler at retrieval.py:263 (`@router.get('/')`) returned
the live RAG pipeline configuration (CHUNK_SIZE, CHUNK_OVERLAP, RAG_TEMPLATE,
RAG_EMBEDDING_ENGINE, RAG_EMBEDDING_MODEL, RAG_RERANKING_MODEL, etc.) without
any authentication dependency, while every adjacent endpoint on the same
router (/embedding, /embedding/update, /config, /config/update) requires
get_admin_user.

Exhaustive search of the repository confirms the endpoint has no callers:

- Frontend (src/): no `RETRIEVAL_API_BASE_URL}/'`-style fetch; the existing
  `getRAGConfig()` in src/lib/apis/retrieval/index.ts targets `/config`,
  not the root, and is the only consumer of admin-level retrieval state.
- Backend self-references: none.
- Cypress e2e (chat, documents, registration, settings): none.
- Backend tests (backend/open_webui/test/): none.
- Build/CI scripts (scripts/): none.
- Direct symbol import of `get_status` from this router: none.

The endpoint is dead code, almost certainly a relic from before the
/config GET split. Removing it has zero UX impact and eliminates the
unauthenticated-config-disclosure surface raised in advisory triage on
GHSA-65pg-qhhw-mxwg. External monitoring scripts that may have hit the
bare root will receive a 404 and can switch to the existing /config
endpoint, which returns the same fields plus the rest of the RAG config
under admin auth.

Surface raised by 0xRyuzak1 in GHSA-65pg-qhhw-mxwg. The advisory was closed
as not-a-vulnerability per SECURITY.md Rule 1 (no security boundary
crossed in default config — RAG_TEMPLATE default is a citation-format
instruction, not a system prompt; no integrity/availability impact); this
removal is independent code-hygiene that aligns the router cohort.

Reported-by: 0xRyuzak1 <https://github.com/0xRyuzak1>

backend/open_webui/routers/retrieval.py

@@ -260,22 +260,6 @@ class SearchForm(BaseModel):
     queries: List[str]
 
 
-@router.get('/')
-async def get_status(request: Request):
-    return {
-        'status': True,
-        'CHUNK_SIZE': request.app.state.config.CHUNK_SIZE,
-        'CHUNK_OVERLAP': request.app.state.config.CHUNK_OVERLAP,
-        'RAG_TEMPLATE': request.app.state.config.RAG_TEMPLATE,
-        'RAG_EMBEDDING_ENGINE': request.app.state.config.RAG_EMBEDDING_ENGINE,
-        'RAG_EMBEDDING_MODEL': request.app.state.config.RAG_EMBEDDING_MODEL,
-        'RAG_RERANKING_MODEL': request.app.state.config.RAG_RERANKING_MODEL,
-        'RAG_EMBEDDING_BATCH_SIZE': request.app.state.config.RAG_EMBEDDING_BATCH_SIZE,
-        'ENABLE_ASYNC_EMBEDDING': request.app.state.config.ENABLE_ASYNC_EMBEDDING,
-        'RAG_EMBEDDING_CONCURRENT_REQUESTS': request.app.state.config.RAG_EMBEDDING_CONCURRENT_REQUESTS,
-    }
-
-
 @router.get('/embedding')
 async def get_embedding_config(request: Request, user=Depends(get_admin_user)):
     return {