fix: DDNS register() always sends public IP and saves token to correct location

Two bugs that prevented registration from working after wizard completion:
1. register(name, '') sent empty IP; server stored blank A record. Now calls
   _get_public_ip() when ip is empty so the A record is always set correctly.
2. Token was saved to _identity.domain.ddns.token (TypeError when domain is a
   string) instead of the top-level ddns config where update_ip() reads it.
   Subdomain also now correctly written to _identity.domain_name.

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

api/ddns_manager.py

@@ -386,27 +386,29 @@ class DDNSManager(BaseServiceManager):
     def register(self, name: str, ip: str) -> dict:
         """Register the cell's subdomain with the configured provider.
 
-        Stores the returned token in the identity config under
-        identity['domain']['ddns']['token'] and records the subdomain.
+        Fetches the public IP via ipify when ip is empty.
+        Stores the returned token in the top-level ddns config (where
+        update_ip reads it) and updates _identity.domain_name.
         Returns the dict from provider.register().
         """
         provider = self.get_provider()
         if provider is None:
             raise DDNSError("No DDNS provider configured")
 
+        if not ip:
+            ip = _get_public_ip() or ''
+
         result = provider.register(name, ip)
 
-        # Persist token + subdomain back into identity
-        identity = self._identity()
-        domain_cfg = dict(identity.get('domain', {}))
-        ddns_cfg = dict(domain_cfg.get('ddns', {}))
-        if 'token' in result:
-            ddns_cfg['token'] = result['token']
-        if 'subdomain' in result:
-            ddns_cfg['subdomain'] = result['subdomain']
-        domain_cfg['ddns'] = ddns_cfg
         if self.config_manager is not None:
-            self.config_manager.set_identity_field('domain', domain_cfg)
+            # Token lives in the top-level ddns config so update_ip() can find it
+            if 'token' in result:
+                ddns_cfg = dict(self.config_manager.configs.get('ddns', {}))
+                ddns_cfg['token'] = result['token']
+                self.config_manager.set_ddns_config(ddns_cfg)
+            # Keep domain_name in identity up to date
+            if 'subdomain' in result:
+                self.config_manager.set_identity_field('domain_name', result['subdomain'])
 
         self._last_ip = ip
         return result