Add per-service customization, stealth hardening, and BYOS support

- HTTP: configurable server_header, response_code, fake_app presets
  (apache/nginx/wordpress/phpmyadmin/iis), extra_headers, custom_body,
  static files directory mount
- SSH/Cowrie: configurable kernel_version, hardware_platform, ssh_banner,
  and users/passwords via COWRIE_USERDB_ENTRIES; switched to build mode
  so cowrie.cfg.j2 persona fields and userdb.txt generation work
- SMTP: configurable banner and MTA hostname
- MySQL: configurable version string in protocol greeting
- Redis: configurable redis_version and os string in INFO response
- BYOS: [custom-*] INI sections define bring-your-own Docker services
- Stealth: rename all *_honeypot.py → server.py; replace HONEYPOT_NAME
  env var with NODE_NAME across all 22+ service templates and plugins;
  strip "honeypot" from all in-container file content
- Config: DeckyConfig.service_config dict; INI [decky-N.svc] subsections;
  composer passes service_cfg to compose_fragment
- 350 tests passing (100%)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

decnet/cli.py

@@ -168,6 +168,7 @@ def _build_deckies_from_ini(
             base_image=distro.image,
             build_base=distro.build_base,
             hostname=hostname,
+            service_config=spec.service_config,
         ))
     return deckies
 
@@ -217,6 +218,20 @@ def deploy(
                       f"[dim]Subnet:[/] {subnet_cidr}  [dim]Gateway:[/] {effective_gateway}  "
                       f"[dim]Host IP:[/] {host_ip}")
 
+        # Register bring-your-own services from INI before validation
+        if ini.custom_services:
+            from decnet.custom_service import CustomService
+            from decnet.services.registry import register_custom_service
+            for cs in ini.custom_services:
+                register_custom_service(
+                    CustomService(
+                        name=cs.name,
+                        image=cs.image,
+                        exec_cmd=cs.exec_cmd,
+                        ports=cs.ports,
+                    )
+                )
+
         effective_log_target = log_target or ini.log_target
         decky_configs = _build_deckies_from_ini(
             ini, subnet_cidr, effective_gateway, host_ip, randomize_services