api_server.py passed "jpg" (no dot) from rsplit, but file_parser.py
parser dict keys all have dots (".jpg"), causing image files to fall
through to _parse_text() which fails on binary data, skipping ALL OCR
and layout analysis. Every image upload was affected.
- file_parser.py: normalize file_type to always have leading dot
- api_server.py: use Path.suffix instead of manual rsplit
- api_server.py: rename 'filename' to 'file_name' in upload_file log extra
dict to avoid collision with Python logging's reserved LogRecord attribute
- test_e2e_ocr.py: replace return statements with assert in test functions
to fix PytestReturnNotNoneWarning