feat(auth): streamline SOPS authentication and network configuration

- Replace age-based key decryption with automatic SSH host key support
- Simplify SSH configuration with consolidated host entries and enhanced security settings
- Upgrade home-manager to himmelblau for Microsoft Entra ID authentication
- Remove legacy agenix inputs and consolidate secrets to essential services only
- Add Cisco Secure Client overlay for enterprise VPN capabilities
- Update secrets.yaml to minimal configuration with gitea/github/hetzner services
- Expand system packages with tun module for VPN connectivity
- Add work directory setup for user development environment

work/default.nix

@@ -0,0 +1,12 @@
+{ config, lib, ... }: {
+  imports = [
+    ./overlay.nix
+    ./cisco.nix
+    ./himmelblau.nix
+  ];
+
+  # Create the work directory for the user
+  systemd.tmpfiles.rules = [
+    "d /home/someone/work 0755 someone users -"
+  ];
+}