chore(deps): add FastAPI web stack (fastapi/uvicorn/jinja2/python-multipart)

New web UI uses these deps; declare them in pyproject + lock so uv sync --frozen
actually installs a runnable environment.

Initial commit: kobo-manga pipeline

Automated manga download-convert-import pipeline for Kobo e-reader.
Plugin-based source architecture, concurrent download engine,
image processing, KEPUB conversion, and device transfer.