feat(mcp): operators can switch MCP (and OAuth) off

Admin switch in the system settings, MCP_ENABLED fixes it. Off: the
endpoint answers 404, OAuth is off, the API key settings hide the MCP tab.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/settings/ApiKeysPanel.tsx

@@ -37,6 +37,8 @@ export const ApiKeysPanel: React.FC<ApiKeysPanelProps> = ({ onIngested }) => {
   const [connectorUrl, setConnectorUrl] = useState('');
   const [copiedConnector, setCopiedConnector] = useState(false);
   const [access, setAccess] = useState<Access>('rest');
+  // The operator can switch MCP off; then only the curl / smart home access is shown
+  const [mcpEnabled, setMcpEnabled] = useState(true);
 
   // Live Webhook Simulator State
   const [simTitle, setSimTitle] = useState('Waschmaschine im Keller ist fertig!');
@@ -59,7 +61,10 @@ export const ApiKeysPanel: React.FC<ApiKeysPanelProps> = ({ onIngested }) => {
     api.getTaskLists().then(setTaskLists).catch(() => {});
     api
       .getAuthStatus()
-      .then((st) => setConnectorUrl(st.mcpConnectorUrl || ''))
+      .then((st) => {
+        setConnectorUrl(st.mcpConnectorUrl || '');
+        setMcpEnabled(st.mcpEnabled !== false);
+      })
       .catch(() => {});
   }, []);
 
@@ -358,30 +363,32 @@ http_headers = { "X-API-Key" = "${exampleToken}" }`
 
       {/* How to connect: one API, two accesses */}
       <div className="pt-4 border-t border-border space-y-4">
-        <div className="flex flex-wrap gap-1.5" role="tablist" aria-label="Zugang">
-          {(
-            [
-              ['rest', 'curl / Smart Home', Terminal],
-              ['mcp', 'KI-Agenten (MCP)', Bot],
-            ] as const
-          ).map(([value, label, Icon]) => (
-            <button
-              key={value}
-              type="button"
-              role="tab"
-              aria-selected={access === value}
-              onClick={() => setAccess(value)}
-              className={`h-11 sm:h-8 px-3 rounded-btn border text-xs flex items-center gap-1.5 transition-colors ${
-                access === value ? 'border-accent bg-accent/10 text-main' : 'border-border text-muted hover:text-main'
-              }`}
-            >
-              <Icon className="w-3.5 h-3.5 text-accent" />
-              {label}
-            </button>
-          ))}
-        </div>
+        {mcpEnabled && (
+          <div className="flex flex-wrap gap-1.5" role="tablist" aria-label="Zugang">
+            {(
+              [
+                ['rest', 'curl / Smart Home', Terminal],
+                ['mcp', 'KI-Agenten (MCP)', Bot],
+              ] as const
+            ).map(([value, label, Icon]) => (
+              <button
+                key={value}
+                type="button"
+                role="tab"
+                aria-selected={access === value}
+                onClick={() => setAccess(value)}
+                className={`h-11 sm:h-8 px-3 rounded-btn border text-xs flex items-center gap-1.5 transition-colors ${
+                  access === value ? 'border-accent bg-accent/10 text-main' : 'border-border text-muted hover:text-main'
+                }`}
+              >
+                <Icon className="w-3.5 h-3.5 text-accent" />
+                {label}
+              </button>
+            ))}
+          </div>
+        )}
 
-        {access === 'rest' && (
+        {(access === 'rest' || !mcpEnabled) && (
           <div className="space-y-5">
             {/* Reading: e.g. a smart home sensor for what is due today */}
             <div>
@@ -547,7 +554,7 @@ http_headers = { "X-API-Key" = "${exampleToken}" }`
           </div>
         )}
 
-        {access === 'mcp' && (
+        {access === 'mcp' && mcpEnabled && (
           <div>
             <div className="flex items-center gap-3 mb-3">
               <div className="w-7 h-7 bg-accent text-on-accent flex items-center justify-center flex-shrink-0">