nginx.conf was hard-capped at 5M, causing 413 on uploads larger than 5MB
despite the backend accepting up to MAX_FILE_SIZE_MB (default 50).
Both nginx configs become envsubst templates. NGINX_MAX_BODY_SIZE defaults
to 200M so the backend application limit is always the effective arbiter.
gettext-base added to the single-image apt deps to provide envsubst.
Prevents PyTorch/Docling pipeline crashes on HF Spaces CPU by:
- Reducing max file size from 50 MB to 5 MB
- Adding configurable MAX_PAGE_COUNT setting (env var, default unlimited)
- Increasing conversion timeout from 600s to 900s
- Adding frontend upload validation with explicit error messages
- Exposing maxPageCount via /api/health for dynamic UI hints
