tests: fix all fail2ban NixOS VM tests

- Add explicit iptables banaction in security.nix for test compatibility
- Force IPv4 in all curl requests to prevent IPv4/IPv6 mismatch issues
- Fix caddy test: use basic_auth directive (not basicauth)
- Override service ports in tests to match direct connections (not via Caddy)
- Vaultwarden: override ROCKET_ADDRESS and ROCKET_LOG for external access
- Immich: increase VM memory to 4GB for stability
- Jellyfin: create placeholder log file and reload fail2ban after startup
- Add tests.nix entries for all 6 fail2ban tests

All tests now pass: ssh, caddy, gitea, vaultwarden, immich, jellyfin

tests/fail2ban-ssh.nix

@@ -0,0 +1,91 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  testServiceConfigs = {
+    zpool_ssds = "";
+    zpool_hdds = "";
+  };
+
+  securityModule = import ../modules/security.nix;
+
+  sshModule =
+    { config, lib, pkgs, ... }:
+    {
+      imports = [
+        (import ../services/ssh.nix {
+          inherit config lib pkgs;
+          username = "testuser";
+        })
+      ];
+    };
+in
+pkgs.testers.runNixOSTest {
+  name = "fail2ban-ssh";
+
+  nodes = {
+    server =
+      { config, lib, pkgs, ... }:
+      {
+        imports = [
+          securityModule
+          sshModule
+        ];
+
+        # Override for testing - enable password auth
+        services.openssh.settings.PasswordAuthentication = lib.mkForce true;
+
+        users.users.testuser = {
+          isNormalUser = true;
+          password = "correctpassword";
+        };
+
+        networking.firewall.allowedTCPPorts = [ 22 ];
+      };
+
+    client = {
+      environment.systemPackages = with pkgs; [ sshpass openssh ];
+    };
+  };
+
+  testScript = ''
+    import time
+
+    start_all()
+    server.wait_for_unit("sshd.service")
+    server.wait_for_unit("fail2ban.service")
+    server.wait_for_open_port(22)
+    time.sleep(2)
+
+    with subtest("Verify sshd jail is active"):
+        status = server.succeed("fail2ban-client status")
+        assert "sshd" in status, f"sshd jail not found in: {status}"
+
+    with subtest("Generate failed SSH login attempts"):
+        # Use -4 to force IPv4, timeout and NumberOfPasswordPrompts=1 to ensure quick failure
+        # maxRetry is 3 in our config, so 4 attempts should trigger a ban
+        for i in range(4):
+            client.execute(
+                "timeout 5 sshpass -p 'wrongpassword' ssh -4 -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o ConnectTimeout=3 -o NumberOfPasswordPrompts=1 testuser@server echo test 2>/dev/null || true"
+            )
+            time.sleep(1)
+
+    with subtest("Verify IP is banned"):
+        # Wait for fail2ban to process the logs and apply the ban
+        time.sleep(5)
+        status = server.succeed("fail2ban-client status sshd")
+        print(f"sshd jail status: {status}")
+        # Check that at least 1 IP is banned
+        import re
+        match = re.search(r"Currently banned:\s*(\d+)", status)
+        assert match and int(match.group(1)) >= 1, f"Expected at least 1 banned IP, got: {status}"
+
+    with subtest("Verify banned client cannot connect"):
+        # Use -4 to test with same IP that was banned
+        exit_code = client.execute("timeout 3 nc -4 -z -w 2 server 22")[0]
+        assert exit_code != 0, "Connection should be blocked for banned IP"
+  '';
+}