Add effects count to home page dashboard

- Add Effects card to home page grid (now 3 columns)
- Add stats["effects"] count from cache.list_by_type('effect')
- Add tests for home page effects display

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/routers/home.py

@@ -65,6 +65,12 @@ async def home(request: Request):
             stats["storage"] = len(storage_providers) if storage_providers else 0
         except Exception:
             pass
+        try:
+            from ..dependencies import get_cache_manager
+            effects = get_cache_manager().list_by_type('effect')
+            stats["effects"] = len(effects)
+        except Exception:
+            pass
 
     templates = get_templates(request)
     return render(templates, "home.html", request,