♻️(frontend) generalize transcript notification for all recording types

Convert transcript-specific toast notification into a flexible component
that works with any recording type. Create extensible design that can
accommodate screen recordings and future recording formats. Implementation
is functional though not perfect, with room for future enhancement.

src/frontend/src/locales/en/notifications.json

@@ -25,5 +25,9 @@
   "transcript": {
     "started": "{{name}} started the meeting transcription.",
     "stopped": "{{name}} stopped the meeting transcription."
+  },
+  "screenRecording": {
+    "started": "{{name}} started the meeting recording.",
+    "stopped": "{{name}} stopped the meeting recording."
   }
 }