fix: propagate dynamic IPs/ports to service pages; add apply restart feedback

Service pages (Email, Calendar, Files) now read IPs and ports from the
config API instead of hardcoded 172.20.0.x constants:
- GET /api/config now includes service_ips (dns, vip_mail, vip_calendar,
  vip_files, vip_webdav) computed from ip_range via ip_utils
- Email.jsx: mailIp, dnsIp, imapPort, smtpPort, webmailPort from context
- Calendar.jsx: calendarIp, dnsIp, calendarPort from context
- Files.jsx: filesIp, webdavIp, webdavPort, filegatorPort from context

Apply button now shows restart progress:
- "Restarting containers — please wait…" spinner while polling /health
- "Containers restarted successfully" on success (clears after 4s)
- "Timed out" / error message if health doesn't come back in 45s

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

webui/src/pages/Calendar.jsx

@@ -3,7 +3,6 @@ import { Calendar as CalendarIcon, Users, Wifi, Copy, CheckCheck } from 'lucide-
 import { calendarAPI } from '../services/api';
 import { useConfig } from '../contexts/ConfigContext';
 
-const CELL_IP = '172.20.0.21';
 
 function CopyButton({ text }) {
   const [copied, setCopied] = useState(false);
@@ -32,8 +31,11 @@ function InfoRow({ label, value }) {
 }
 
 function Calendar() {
-  const { domain = 'cell' } = useConfig();
-  const cellHost = `calendar.${domain}`;
+  const { domain = 'cell', service_ips = {}, service_configs = {} } = useConfig();
+  const cellHost    = `calendar.${domain}`;
+  const calendarIp  = service_ips.vip_calendar || '172.20.0.21';
+  const dnsIp       = service_ips.dns           || '172.20.0.3';
+  const calendarPort = service_configs.calendar?.port ?? 5232;
   const [users, setUsers] = useState([]);
   const [status, setStatus] = useState(null);
   const [isLoading, setIsLoading] = useState(true);
@@ -87,11 +89,12 @@ function Calendar() {
             <InfoRow label="CalDAV path"   value={`http://${cellHost}/`} />
             <InfoRow label="CardDAV path"  value={`http://${cellHost}/`} />
             <InfoRow label="Port"          value="80" />
-            <InfoRow label="Direct IP"     value={CELL_IP} />
+            <InfoRow label="Direct IP"     value={calendarIp} />
+            <InfoRow label="Direct port"   value={String(calendarPort)} />
             <InfoRow label="Protocol"      value="HTTP (CalDAV/CardDAV)" />
           </div>
           <p className="text-xs text-gray-400 mt-3">
-            Requires VPN connection. DNS server must be set to <span className="font-mono">172.20.0.3</span>.
+            Requires VPN connection. DNS server must be set to <span className="font-mono">{dnsIp}</span>.
           </p>
         </div>