fix(privacy): sanitize console error/warn to prevent PII leakage

Replace raw error object logging (which may contain Matrix event
payloads, user IDs, or message bodies) with e.message-only strings
in three files:
- CallEmbed.ts: state update and event widget feed errors
- msgContent.ts: image/video element load failures and thumb errors
- RoomInput.tsx: GIF send failure

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/RoomInput.tsx

@@ -725,7 +725,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
             info: { mimetype: 'image/gif', w, h, size: blob.size },
           });
         } catch (e) {
-          console.error('GIF send failed', e);
+          console.error('GIF send failed:', e instanceof Error ? e.message : 'unknown error');
           if (!alive()) return;
           setGifError('Failed to send GIF. Please try again.');
           setTimeout(() => setGifError(null), 4000);