Update flake.lock (#539)

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/b6208f5' (2026-03-06)
  → 'github:cachix/devenv/b928544' (2026-03-08)
• Updated input 'fenix':
    'github:nix-community/fenix/37e7356' (2026-03-06)
  → 'github:nix-community/fenix/6bcc99c' (2026-03-07)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/2a8f00f' (2026-03-05)
  → 'github:rust-lang/rust-analyzer/fad5c3d' (2026-03-06)
• Updated input 'nix-index-db':
    'github:nix-community/nix-index-database/a2051ff' (2026-03-01)
  → 'github:nix-community/nix-index-database/1c1d8ea' (2026-03-08)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/80bdc1e' (2026-03-04)
  → 'github:NixOS/nixpkgs/aca4d95' (2026-03-06)
• Updated input 'nixpkgs-stable':
    'github:NixOS/nixpkgs/230ac09' (2026-03-06)
  → 'github:NixOS/nixpkgs/aa1e6ad' (2026-03-06)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/c10801f' (2026-03-07)
  → 'github:oxalica/rust-overlay/bb93f19' (2026-03-08)
• Updated input 'sops-nix':
    'github:Mic92/sops-nix/1d9b98a' (2026-03-02)
  → 'github:Mic92/sops-nix/c8e6967' (2026-03-08)
```

### 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]