feat: Phase 6 — require_active_service decorator + wizard install wiring

Email/calendar/files routes now return 404 when the service is not
installed, using a require_active_service decorator that checks
ServiceRegistry. Status endpoints are exempt so health checks always work.

SetupManager.complete_setup() now accepts a service_store_manager and
installs any wizard-selected services in a background daemon thread after
setup completes. Failures are logged but do not fail the wizard.

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

api/managers.py

@@ -66,7 +66,6 @@ cell_link_manager  = CellLinkManager(
     network_manager=network_manager,
 )
 auth_manager = AuthManager(data_dir=DATA_DIR, config_dir=CONFIG_DIR)
-setup_manager = SetupManager(config_manager=config_manager, auth_manager=auth_manager)
 caddy_manager = CaddyManager(config_manager=config_manager, data_dir=DATA_DIR, config_dir=CONFIG_DIR,
                               service_bus=service_bus, service_registry=service_registry)
 ddns_manager = DDNSManager(config_manager=config_manager, data_dir=DATA_DIR, config_dir=CONFIG_DIR)
@@ -96,6 +95,9 @@ service_store_manager = ServiceStoreManager(
     service_composer=service_composer,
 )
 
+setup_manager = SetupManager(config_manager=config_manager, auth_manager=auth_manager,
+                             service_store_manager=service_store_manager)
+
 # Service logger configuration
 _service_log_configs = {
     'network':   {'level': 'INFO', 'formatter': 'json', 'console': False},