feat: show tag counts alongside doc counts on dashboard

Fetch /api/tags/ in parallel with /api/documents/ for each instance.
Dashboard now displays "X docs, Y tags" per master/replica.

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

app/api/status.py

@@ -89,13 +89,13 @@ def get_status(session: Session = Depends(get_session)):
     }
 
 
-async def _fetch_count(url: str, token: str) -> int | None:
+async def _fetch_count(url: str, token: str, path: str = "/api/documents/") -> int | None:
     import httpx
     try:
         async with httpx.AsyncClient(
             headers={"Authorization": f"Token {token}"}, timeout=8.0
         ) as client:
-            r = await client.get(url.rstrip("/") + "/api/documents/", params={"page_size": 1})
+            r = await client.get(url.rstrip("/") + path, params={"page_size": 1})
             r.raise_for_status()
             return r.json().get("count")
     except Exception: