Deprecate and remove MediaContainerV3 - incomplete V2 migration component

[cameronsjo]

Issue

MediaContainerV3.tsx is an incomplete/experimental component from the V2 API migration that should be deprecated and removed.

Problems Identified

1. Architectural Mismatch: Tries to use V2 API with legacy V1 components (MediaLightbox)
2. Incomplete Implementation: Missing critical features:
   • User ratings management
   • Queue management
   • Media parsing infrastructure
   • Copy file IDs functionality
3. API Signature Errors (4 TypeScript errors):
   • useV2MediaActions() called without required props
   • Uses non-existent hideMedia (should be hideMediaEverywhere/hideMediaInPosts)
   • Uses non-existent updateTags (should be addMediaTags/removeMediaTags)
   • Calls likeMedia(id, {rating: 1}) but signature is likeMedia(id)
   • MediaLightbox missing 6+ required props

Root Cause

This component represents transitional code from the V2 migration that was never completed. It attempts to bridge V2 MediaFile entities with legacy post-based infrastructure.

Recommendation

DEPRECATE this component rather than fix it:

1. Add deprecation notice to file
2. Identify usages (ModernMediaGrid uses it)
3. Migrate ModernMediaGrid to use MediaContainerWithContext or create V2-native lightbox
4. Remove MediaContainerV3 once migration complete

Better Alternatives

• MediaContainer - Full-featured, production-ready
• MediaContainerWithContext - Context-aware wrapper
• Future: Build V2-native lightbox component that works with MediaFile directly

Files Affected

• apps/frontend/src/features/media/components/MediaContainerV3.tsx
• apps/frontend/src/features/media/components/ModernMediaGrid.tsx (uses it)