Add new server modules and configurations for various services

- Introduced `default-creds` module for managing default credentials with Umami integration.
- Added `fail2ban` module for brute-force attack protection with configurable ban times.
- Created `firewall` module to enable and configure basic firewall settings.
- Implemented `gitea` module for self-hosted Git service with PostgreSQL backend.
- Developed `glance` module for a customizable dashboard with various widgets and themes.
- Added `iknowyou` module for a self-hosted password manager with production and demo environments.
- Introduced `kernel-hardening` module for enhancing kernel security settings.
- Created `mazanoke` module for a simple web application with Nginx integration.
- Added `mealie` module for a self-hosted meal planning application.
- Implemented `stirling-pdf` module for PDF generation service.
- Developed `umami` module for self-hosted analytics with secret management.
- Added `ssh` module for secure SSH configuration with user restrictions.
- Introduced `nixy` theme for a customized aesthetic experience across services.

docs/THEMES.md

@@ -0,0 +1,17 @@
+# Themes
+
+Themes are defined in `themes`. Those themes define the colors, fonts, icons, etc, used by Hyprland and the apps/programs installed.
+You can change the selected theme by changing the import statement of your host's variables.nix file.
+
+## Create your theme
+
+Create a copy of one of the existing themes and change the variables.
+Wallpapers are loaded from the [hadi's awesome-wallpapers](https://github.com/anotherhadi/awesome-wallpapers) repo.
+
+## Gallery
+
+### Rose-pine
+
+![Home](../.github/assets/rose-pine/home.png)
+![Flake & Spotify](../.github/assets/rose-pine/flake-spotify.png)
+![Browser and notification center](../.github/assets/rose-pine/browser-and-notifications.png)