Live wall: pinned/docked cameras stop when their provider is switched off; admin-only empty-state CTA

- LiveView: localStorage pins carry image URLs, so they rendered (without
  credit) after an admin disabled the provider. Pins now show only while
  their provider is serving (server-26#198 licence gating).
- MapView: pinned/docked map players drop out once their provider leaves
  the serving list; credits are kept from the last answer so docked players
  keep attribution while the overlay is hidden.
- WallPanels: the "no camera provider enabled" link to /admin was a dead CTA
  for non-admins (bounced to /). Link shown to admins only, deep-linked to
  /admin#cameras; the admin page now honours a tab hash.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/components/MapView.tsx

@@ -564,8 +564,16 @@ function DotCameraLayer({ onOpenCamera }: { onOpenCamera?: (c: Camera) => void }
   const shown = useOverlayShown(map, OVERLAY_DOT_CAMERAS);
   const zoom = useMapZoom(map);
   const { data, error, loaded } = useMapCameras(map, shown);
-  const [open, setOpen] = useState<OpenCamera[]>([]);
-  const feeds = useMemo(() => creditsByProvider(data.providers), [data.providers]);
+  const [openAll, setOpen] = useState<OpenCamera[]>([]);
+  // Credits from the last answer received while the overlay was on. Hiding the
+  // overlay empties `data`, but docked players stay up and still need their
+  // attribution. A pinned/docked camera whose provider an admin has since
+  // switched off (licence gating, server-26#198) drops out on the next answer.
+  const [feeds, setFeeds] = useState<Map<string, CameraProviderFeed>>(() => new Map());
+  useEffect(() => {
+    if (shown && loaded) setFeeds(creditsByProvider(data.providers));
+  }, [shown, loaded, data.providers]);
+  const open = useMemo(() => openAll.filter((o) => feeds.has(o.cam.provider)), [openAll, feeds]);
 
   const pinnedIds = useMemo(() => new Set(open.filter((o) => o.mode === "pin").map((o) => o.cam.id)), [open]);
   const cells = useMemo(