feat: initial release — pdf-toolkit v1.0.0

Core operations:
- Compress PDF (3 presets: screen, ebook, printer, prepress)
- PDF/A detection and conversion to regular PDF
- Compress while preserving PDF/A structure
- Merge multiple PDFs
- Split/extract pages by range
- Rotate pages
- Extract text and images

Interface:
- Streamlit web GUI (app.py)
- FastAPI REST API with auto OpenAPI docs (api.py)

Docs:
- README.md, ARCHITECTURE.md, API.md
- Unit tests (15/15 passing)

.gitignore

@@ -0,0 +1,13 @@
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.env
+.env.local
+venv/
+.venv/
+tmp/
+*.egg-info/
+dist/
+build/
+.pytest_cache/