⚡️(admin) remove list filters based on room in recording view

This was a mistake: the filter was never used in production and caused
performance issues. It generated a list of unique room slugs, bloating the DOM
with thousands of values and slowing down view rendering. Remove this
regression.

src/backend/core/admin.py

@@ -207,7 +207,7 @@ class RecordingAdmin(admin.ModelAdmin):
         "created_at",
         "worker_id",
     )
-    list_filter = ["status", "room", "created_at"]
+    list_filter = ["created_at"]
     readonly_fields = ["id", "created_at", "updated_at"]
     actions = [resend_notification]