Simplify client proxy port handling

src/web/components/ClientOverviewPage.jsx

@@ -203,6 +203,7 @@ function ProxySettings({ state, settings, busy, onSave }) {
   const parsed = Number.parseInt(draftPort, 10);
   const invalid = !Number.isInteger(parsed) || parsed < range.start || parsed > range.end;
   const dirty = !invalid && parsed !== port;
+  const singlePublishedPort = range.start === range.end;
 
   return (
     <aside className="client-side-panel">
@@ -222,17 +223,20 @@ function ProxySettings({ state, settings, busy, onSave }) {
             min={range.start}
             max={range.end}
             value={draftPort}
+            disabled={singlePublishedPort}
             onChange={(e) => setDraftPort(e.target.value)}
           />
           <button
             className="btn btn-secondary"
-            disabled={busy || !dirty}
+            disabled={busy || singlePublishedPort || !dirty}
             onClick={() => onSave({ ...settings, proxyPort: parsed })}
           >
             Save
           </button>
         </div>
-        <small className={invalid ? 'field-error' : 'field-hint'}>{range.start}–{range.end}</small>
+        <small className={invalid ? 'field-error' : 'field-hint'}>
+          {singlePublishedPort ? 'Порт задаётся установщиком' : `${range.start}–${range.end}`}
+        </small>
       </div>
     </aside>
   );