fix: use configured domain in CoreDNS Corefile generation

Two bugs caused DNS to fail when the domain name changes:
1. generate_corefile() hardcoded 'cell' as the zone name instead of
   using the configured domain — on startup it would silently reset any
   domain change back to 'cell'
2. apply_domain() regex replaced ALL non-dot zones (including local.cell)
   with the new domain → duplicate zone blocks → CoreDNS crash

Fix: add a domain parameter to generate_corefile/apply_all_dns_rules,
add _configured_domain() helper in app.py, and delegate Corefile updates
in apply_domain() to generate_corefile() so the logic is in one place.
Also parameterise SERVICE_HOSTS ACL entries via the domain argument.

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

api/network_manager.py

@@ -401,30 +401,17 @@ class NetworkManager(BaseServiceManager):
         except Exception as e:
             warnings.append(f"dnsmasq domain update failed: {e}")
 
-        # 2. Update Corefile: replace old primary zone block with new domain
+        # 2. Regenerate Corefile using generate_corefile so it always stays consistent
         try:
+            import firewall_manager as _fm
             corefile = os.path.join(self.config_dir, 'dns', 'Corefile')
-            if os.path.exists(corefile):
-                with open(corefile) as f:
-                    content = f.read()
-                import re
-                # Replace first named zone block (not the catch-all .) with new domain
-                # Matches: <word> { ... } blocks (zone names like "cell", "oldname")
-                def replace_zone(m):
-                    zone = m.group(1)
-                    if zone == '.':
-                        return m.group(0)  # keep catch-all
-                    # Replace zone name with new domain; update file path reference
-                    body = m.group(2)
-                    body = re.sub(r'file\s+/data/\S+\.zone',
-                                  f'file /data/{domain}.zone', body)
-                    return f'{domain} {{{body}}}'
-                new_content = re.sub(
-                    r'(\S+)\s*\{([^}]*)\}',
-                    replace_zone, content, flags=re.DOTALL
-                )
-                with open(corefile, 'w') as f:
-                    f.write(new_content)
+            peers_file = os.path.join(self.data_dir, 'peers.json')
+            try:
+                import json as _json
+                peers = _json.loads(open(peers_file).read()) if os.path.exists(peers_file) else []
+            except Exception:
+                peers = []
+            _fm.generate_corefile(peers, corefile, domain)
         except Exception as e:
             warnings.append(f"Corefile domain update failed: {e}")