fix: all service pages use live domain; cell_name/domain propagate to DNS; /api/status reads stored identity

Changes:
- ConfigContext.jsx: React context that loads /api/config once; exposes domain,
  cell_name, refresh() — wraps entire app in App.jsx
- Email/Calendar/Files pages: replace hardcoded 'mail.cell', 'calendar.cell',
  'files.cell', 'webdav.cell' with domain from ConfigContext; hostname updates
  immediately after Settings save (refreshConfig() called on save)
- /api/status: cell_name and domain now read from stored _identity in config_manager,
  not hardcoded 'personal-internet-cell' / 'cell.local'
- network_manager.apply_cell_name(old, new): updates hostname A-record in primary
  zone file and reloads CoreDNS; called from PUT /api/config when cell_name changes
- Old identity captured before save so apply_cell_name gets the correct old value
- Settings EmailForm: smtp/imap ports are read-only with note (docker-compose.yml level)
- Settings FilesForm: port is read-only with note (Caddy proxies on 80 externally)
- Settings CalendarForm: port labeled "Internal port; clients use 80 via Caddy"

Tests added:
- test_apply_cell_name_renames_host_record
- test_apply_cell_name_noop_when_same

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

api/app.py

@@ -356,9 +356,10 @@ def get_cell_status():
         current_time = time.time()
         uptime_seconds = int(current_time - API_START_TIME)
         
+        identity = config_manager.configs.get('_identity', {})
         return jsonify({
-            "cell_name": "personal-internet-cell",
-            "domain": "cell.local",
+            "cell_name": identity.get('cell_name', os.environ.get('CELL_NAME', 'mycell')),
+            "domain": identity.get('domain', os.environ.get('CELL_DOMAIN', 'cell')),
             "uptime": uptime_seconds,
             "peers_count": len(peers),
             "services": services_status,
@@ -397,6 +398,8 @@ def update_config():
         # Handle identity fields (cell_name, domain, ip_range, wireguard_port)
         identity_keys = {'cell_name', 'domain', 'ip_range', 'wireguard_port'}
         identity_updates = {k: v for k, v in data.items() if k in identity_keys}
+        # Capture old identity BEFORE saving, for apply_cell_name comparison
+        old_identity = dict(config_manager.configs.get('_identity', {}))
         if identity_updates:
             stored = config_manager.configs.get('_identity', {})
             stored.update(identity_updates)
@@ -439,6 +442,15 @@ def update_config():
             all_restarted.extend(net_result.get('restarted', []))
             all_warnings.extend(net_result.get('warnings', []))
 
+        # Apply cell name change to DNS hostname record
+        if identity_updates.get('cell_name'):
+            old_name = old_identity.get('cell_name', os.environ.get('CELL_NAME', 'mycell'))
+            new_name = identity_updates['cell_name']
+            if old_name != new_name:
+                cn_result = network_manager.apply_cell_name(old_name, new_name)
+                all_restarted.extend(cn_result.get('restarted', []))
+                all_warnings.extend(cn_result.get('warnings', []))
+
         logger.info(f"Updated config, restarted: {all_restarted}")
         return jsonify({
             "message": "Configuration updated and applied",