feat: Add comprehensive keyboard shortcuts system for video editor

- Implement industry-standard video editing shortcuts (Space, J/K/L, arrows)
- Add playback controls: Space (play/pause), J/K/L (rewind/pause/forward)
- Add navigation: arrow keys (frame stepping), Shift+arrows (5s jumps), Home/End
- Add editing shortcuts: S (split at playhead), N (toggle snapping)
- Add selection shortcuts: Ctrl/Cmd+A (select all), Ctrl/Cmd+D (duplicate)
- Add keyboard shortcuts help dialog with categorized shortcuts display
- Integrate help button in editor header for discoverability
- Add TypeScript type declarations for better development experience
- Fix Docker build environment variable validation issues

All shortcuts follow professional video editing standards (Avid/Premiere/Final Cut).
Context-aware shortcuts that don't interfere with text input fields.
Toast notifications provide user feedback for better UX.

apps/web/Dockerfile

@@ -21,6 +21,12 @@ COPY packages/auth/ packages/auth/
 
 ENV NODE_ENV production
 ENV NEXT_TELEMETRY_DISABLED 1
+# Set build-time environment variables for validation
+ENV DATABASE_URL="postgresql://opencut:opencutthegoat@localhost:5432/opencut"
+ENV BETTER_AUTH_SECRET="build-time-secret"
+ENV UPSTASH_REDIS_REST_URL="http://localhost:8079"
+ENV UPSTASH_REDIS_REST_TOKEN="example_token"
+ENV NEXT_PUBLIC_BETTER_AUTH_URL="http://localhost:3000"
 
 WORKDIR /app/apps/web
 RUN bun run build