Upgrade NixOS Release

Upgrade NixOS to a new stable release version. This involves updating version-pinned flake inputs and handling any breaking changes.

Process

Check current state
```
nixos-version
nix --version
```
Identify version-pinned inputs in flake/flake.nix that need updating:
- nixpkgs (e.g., nixos-25.05 → nixos-25.11)
- home-manager (e.g., release-25.05 → release-25.11)
- nix-darwin (e.g., nix-darwin-25.05 → nix-darwin-25.11)
- stylix (e.g., release-25.05 → release-25.11)