fix(media-manager): resolve video preview issues and stabilize tests

- Backend (MediaService):
    - Implemented robust contentUrl generation for Drive files using drive.google.com/uc pattern.
    - Added mimeType exposure to unified media state.

- Frontend (MediaManager):
    - Replaced video tag with iframe embedding the Google Drive Preview player (/preview) for reliable playback.
    - Fixed syntax error in console logging causing UI freeze.
    - Updated gallery card logic to prioritize video content URLs.

- Tests (Integration):
    - Refactored mediaManager.integration.test.ts to align with new logic.
    - Mocked DriveApp completely to support orphan adoption flows.
    - Updated file renaming expectations to support timestamped filenames.

- Documentation:
    - Updated MEMORY.md with video preview strategy.

src/services/MockDriveService.ts

@@ -50,6 +50,8 @@ export class MockDriveService implements IDriveService {
         getUrl: () => `https://mock.drive/files/${blob.getName()}`,
         getLastUpdated: () => new Date(),
         getThumbnail: () => ({ getBytes: () => [] }),
+        getMimeType: () => (blob as any).getContentType ? (blob as any).getContentType() : "image/jpeg",
+        getDownloadUrl: () => `https://drive.google.com/uc?export=download&id=${id}`,
         getAppProperty: (key) => {
              return (newFile as any)._properties?.[key]
         }