build: consolidate Dependabot updates — uvicorn[standard] floor >=0.50.0 -> >=0.51.0 (#46), ruff 0.15.20 -> 0.15.21 (#45), mypy 2.1.0 -> 2.2.0 (#44). Dev/build tooling + ASGI-server bumps only; no runtime behavior or API change. make ci-local green under the new toolchain.
