feat(framework): Enable FastAPI to manage SuperLinkLifespan

[danieljanes]

Merge after #7499

[Copilot]

Pull request overview

Adds an initial FastAPI-based HTTP API scaffold for SuperLink/SuperNode within framework/py/flwr, along with dependency updates to support running these apps via uvicorn.

Changes:

• Add FastAPI app entrypoints for SuperLink and SuperNode, wiring in new router modules (health/control/runtime).
• Update rest optional dependencies to include FastAPI (and bump Starlette/Uvicorn versions), and refresh uv.lock.
• Add a short FASTAPI.md with install/run instructions.

Critical issues

• Stub endpoints currently return HTTP 200 with a "not_implemented" body; they should return an HTTP error status (e.g., 501) so clients/tooling don’t treat these as successful responses. (PR comments: IDs 003–005)
• FastAPI(..., version="1.32.0") is hard-coded in both apps and can drift from flwr.__version__. (PR comments: IDs 001–002)

Simplicity/readability suggestions

• rest now depends on fastapi[standard], which pulls in significant transitive tooling not used by the scaffold in this PR; consider depending on plain fastapi (or splitting into a separate extra) to keep the optional dependency footprint smaller. (PR comment: ID 006)

Consistency concerns

• framework/FASTAPI.md uses uv sync --all-extras; other framework docs recommend uv sync --locked ... for reproducible installs. (PR comment: ID 007)

Whether the PR should be split

No—these changes are all in service of introducing the FastAPI scaffold and its dependency/docs wiring.

Overall verdict

Changes are needed before approval.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
framework/uv.lock	Locks new REST/FastAPI dependency set (FastAPI, updated Starlette/Uvicorn, transitive deps).
framework/pyproject.toml	Updates rest optional dependencies to include FastAPI and newer Starlette/Uvicorn pins.
framework/py/flwr/supercore/routers/__init__.py	Introduces core router package for shared endpoints.
framework/py/flwr/supercore/routers/health/__init__.py	Exposes the health router.
framework/py/flwr/supercore/routers/health/router.py	Adds /health endpoint router.
framework/py/flwr/superlink/main.py	Adds SuperLink FastAPI app and includes routers.
framework/py/flwr/superlink/routers/__init__.py	Introduces SuperLink router package.
framework/py/flwr/superlink/routers/control/__init__.py	Exposes the control router.
framework/py/flwr/superlink/routers/control/router.py	Adds stub control route(s).
framework/py/flwr/superlink/routers/runtime/__init__.py	Exposes the runtime router.
framework/py/flwr/superlink/routers/runtime/router.py	Adds stub runtime route(s).
framework/py/flwr/supernode/main.py	Adds SuperNode FastAPI app and includes routers.
framework/py/flwr/supernode/routers/__init__.py	Introduces SuperNode router package.
framework/py/flwr/supernode/routers/runtime/__init__.py	Exposes the runtime router.
framework/py/flwr/supernode/routers/runtime/router.py	Adds stub runtime route(s).
framework/FASTAPI.md	Adds install/run instructions for the new FastAPI apps.

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