FEAT: Add ArabicPresentationFormConverter for Arabic isolated-form substitution

[Raulster24]

Description

Adds ArabicPresentationFormConverter, a deterministic PromptConverter that substitutes Arabic letters with their isolated Arabic Presentation Forms-B glyphs (for example ALEF U+0627 -> U+FE8D). A reader still recognizes the same letters, shown in their non-joining isolated shapes, while the underlying code point and token sequence change. The substitution map is derived from Unicode decomposition data (not hand-maintained), so it stays correct across Unicode versions. Characters with no Arabic isolated presentation form (including Arabic digits and punctuation) are left unchanged.

Third in a small set of atomic Arabic-script converters, following BidiConverter (#1832) and TatweelConverter (#1869). This is a character-substitution converter and can later migrate to a shared CharacterSubstitutionConverter base alongside the planned ArabiziConverter.

cc @romanlutz

Tests and Documentation

• Added tests/unit/prompt_converter/test_arabic_presentation_form_converter.py: exact mapping, non-Arabic passthrough, mixed text, Arabic-non-letter (digit/punctuation) passthrough, empty input, determinism, and unsupported-input-type rejection. All pass: uv run pytest tests/unit/prompt_converter/test_arabic_presentation_form_converter.py
• Registered in pyrit/prompt_converter/__init__.py (import + __all__).
• Added a usage example to doc/code/converters/1_text_to_text_converters.py and regenerated the paired .ipynb plus the converter modality table in 0_converters.ipynb via JupyText.
• ruff and ty are clean; the converter-documentation conformance test passes.