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.

server-modules/ssh.nix

@@ -0,0 +1,37 @@
+# SSH configuration
+{config, ...}: let
+  username = config.var.username;
+in {
+  services.openssh = {
+    enable = true;
+    ports = [22];
+    openFirewall = true;
+    settings = {
+      PermitRootLogin = "no";
+      PasswordAuthentication = false;
+      AllowUsers = [username];
+      MaxAuthTries = 3;
+      LoginGraceTime = 20;
+      X11Forwarding = false;
+      AllowAgentForwarding = false;
+      AllowTcpForwarding = false;
+      ClientAliveInterval = 300;
+      ClientAliveCountMax = 2;
+      KexAlgorithms = [
+        "curve25519-sha256"
+        "curve25519-sha256@libssh.org"
+      ];
+      Ciphers = [
+        "chacha20-poly1305@openssh.com"
+        "aes256-gcm@openssh.com"
+      ];
+    };
+  };
+
+  # Add my public SSH key to my user
+  users.users."${username}".openssh.authorizedKeys.keys = [
+    "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPG9SE80ZyBcXZK/f5ypSKudaM5Jo3XtQikCnGo0jI5E hadi@nixy"
+  ];
+
+  services.cloudflared.tunnels."${config.var.tunnelId}".ingress."ssh.${config.var.domain}" = "ssh://localhost:22";
+}