Revert to OPUS-MT translation by default - better name handling

Improve translation completeness: better paragraph splitting for headings, improved prompts, lower min length for titles

Add validation to prevent translating worship program files instead of sermon transcripts

Fix: Save bilingual file to current directory, prevent PDF/bilingual file duplication, ensure Message section only uses bilingual content

Integrate improved Qwen2.5 translation into document_processing_agent with fallback to OPUS-MT

Initial commit for HF Space deployment