uv version management is all over the place

We manage uv version using mechanics such as:

- https://github.com/Flagsmith/flagsmith/blob/13eeb4687959c1f730b20eb440c3c3523d53878c/.github/actions/install-uv/action.yml#L20
- https://github.com/Flagsmith/flagsmith/blob/13eeb4687959c1f730b20eb440c3c3523d53878c/api/pyproject.toml#L161
- https://github.com/Flagsmith/flagsmith/blob/13eeb4687959c1f730b20eb440c3c3523d53878c/mcp/pyproject.toml#L38
- https://github.com/Flagsmith/flagsmith/blob/13eeb4687959c1f730b20eb440c3c3523d53878c/.pre-commit-config.yaml#L74
- Other untraced occasions?

## Acceptance criteria

1. Renovate manages uv a unified version repository-wide.

Start by comparing the uv version references in .github/actions/install-uv/action.yml, api/pyproject.toml, mcp/pyproject.toml, and .pre-commit-config.yaml, then search the repository for additional uv references and inspect the existing Renovate configuration. Done means Renovate manages one unified uv version repository-wide.

Written by the indexing model from the issue text.