Add list_networks, create_network, delete_network tools (Gruppe 4)

list_networks:
  SYNO.Docker.Network/list → shows name, driver, subnet, gateway,
  attached containers. Response key is "network" (not "networks").

create_network(name, driver, subnet, gateway, ip_range, enable_ipv6, confirmed):
  Dry-run preview without confirmed=True. Passes enable_ipv6 as
  json.dumps(bool) per N4S4 reference. Optional params (subnet,
  gateway, iprange) omitted from request when not provided.

delete_network(name, confirmed):
  Validates network exists and has no attached containers before
  deleting. Clear error listing attached container names if blocked.

15 unit tests covering all paths.

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

src/mcp_synology_container/server.py

@@ -29,6 +29,7 @@ def create_server(config: AppConfig, client: DsmClient) -> FastMCP:
     from mcp_synology_container.modules.compose import register_compose
     from mcp_synology_container.modules.containers import register_containers
     from mcp_synology_container.modules.images import register_images
+    from mcp_synology_container.modules.networks import register_networks
     from mcp_synology_container.modules.projects import register_projects
     from mcp_synology_container.modules.system import register_system
 
@@ -37,6 +38,7 @@ def create_server(config: AppConfig, client: DsmClient) -> FastMCP:
     register_compose(mcp, config, client)
     register_images(mcp, config, client)
     register_system(mcp, config, client)
+    register_networks(mcp, config, client)
 
     logger.info("MCP server configured with all tool modules")
     return mcp