feat: add support for Falcon-OCR (#3237)

* feat: add support for Falcon-OCR (tiiuae/Falcon-OCR)

Add Falcon-OCR as a VLM convert model for document OCR and markdown
conversion. Falcon-OCR is a 0.3B parameter model from TII that supports
full-page text extraction, formula (LaTeX), and table (HTML) recognition.

Changes:
- Add VLM_CONVERT_FALCON_OCR preset (stage_model_specs.py)
- Add legacy specs: FALCON_OCR_TRANSFORMERS, FALCON_OCR_VLLM,
  FALCON_OCR_VLLM_API (vlm_model_specs.py)
- Register preset with VlmConvertOptions (pipeline_options.py)
- Fix trust_remote_code propagation from VlmModelSpec to engine options
  in auto_inline_engine.py and from_preset(), which also fixes the
  existing Phi-4 preset
- Add test suite (tests/test_falcon_ocr_vlm.py)

Closes: docling-project/docling#3236

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* style: apply ruff formatting

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* fix: align Falcon-OCR presets with review feedback

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

---------

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>