Align top-level backend routes to support image-only content (week>=3), remove legacy content-required validations

Update backend submodule with auto-initialization fix

Update backend submodule with SourceText model changes

Update frontend submodule with definitive Week 2 timecodes

Update Week 2 video subtitling with definitive cross-platform timecodes - All 26 segments updated with precise millisecond accuracy for Mac/Windows compatibility

Update deploy/frontend submodule with syntax fix

Update deploy/frontend submodule with image upload functionality

Restore image upload functionality for Week 2 tutorial tasks

Resolve merge conflicts and fix WeeklyPractice.tsx

Fix TypeScript compilation error: Move subtitleSegments declaration before useEffect usage

Version 2.0: Translation brief and image upload functionality working, Week 1 preserved

Fix TypeScript errors for image support in Week 2 tutorial tasks