fix(batch,static): resolve batch processing and host mount static file issues
Batch Processing Fixes:
- Fix database session isolation causing badge processors to create temporary sessions
- Replace _process_with_isolated_connection with _process_with_shared_session in pipeline
- Add robust error handling to prevent single poster failures from terminating batch
- Improve progress logging and add poster-by-poster status tracking
- Add small delays between poster processing to prevent system overload
Static File Serving Fixes:
- Ensure directories exist before mounting static files (critical for host mounts)
- Add proper error logging for missing static directories
- Create setup scripts for host directory structure (setup-host-dirs.sh/ps1)
Resolves issues where:
- Batch jobs would process only the first poster then silently stop
- Preview images wouldn't display when using host directory mounts instead of volumes
All batch posters now process correctly and static files serve properly with host mounts.