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)

requirements.txt

@@ -0,0 +1,6 @@
+streamlit>=1.30
+fastapi>=0.100
+uvicorn[standard]>=0.20
+pypdf>=5
+Pillow>=10
+python-multipart>=0.0.6