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/tests.nix

@@ -12,4 +12,12 @@ in
   testTest = handleTest ./testTest.nix;
   minecraftTest = handleTest ./minecraft.nix;
   jellyfinQbittorrentMonitorTest = handleTest ./jellyfin-qbittorrent-monitor.nix;
+
+  # fail2ban tests
+  fail2banSshTest = handleTest ./fail2ban-ssh.nix;
+  fail2banCaddyTest = handleTest ./fail2ban-caddy.nix;
+  fail2banGiteaTest = handleTest ./fail2ban-gitea.nix;
+  fail2banVaultwardenTest = handleTest ./fail2ban-vaultwarden.nix;
+  fail2banImmichTest = handleTest ./fail2ban-immich.nix;
+  fail2banJellyfinTest = handleTest ./fail2ban-jellyfin.nix;
 }