Update flake.lock (#543)

Automated changes by the
[update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock)
GitHub Action.

```
Flake lock file updates:

• Updated input 'devenv':
    'github:cachix/devenv/0a7c490' (2026-03-11)
  → 'github:cachix/devenv/2e5cfe2' (2026-03-12)
• Updated input 'fenix':
    'github:nix-community/fenix/64407dd' (2026-03-10)
  → 'github:nix-community/fenix/42f953f' (2026-03-11)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/16e4436' (2026-03-09)
  → 'github:rust-lang/rust-analyzer/e0269ce' (2026-03-10)
• Updated input 'home-manager':
    'github:nix-community/home-manager/3f98e2b' (2026-03-10)
  → 'github:nix-community/home-manager/7d06e0c' (2026-03-12)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/e552b1d' (2026-03-11)
  → 'github:oxalica/rust-overlay/2b18fe4' (2026-03-12)
```

### Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened
by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

```sh
git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force
```

Author: github-actions[bot]