feat: add unified Settings sheet, MCP indicator, and Docker host config

- Add AppSettingsSheet (gear icon in Toolbar) with MCP, Docker, and AI sections
- MCP Server: toggle on/off, port config, status badge, endpoint URL with copy
- Docker: local/remote daemon selector with remote URL input
- AI: moved Ollama settings into the unified sheet
- MCP status probes actual TCP port for reliable running detection
- Docker commands respect configurable docker host (-H flag) for remote daemons
- MCP server supports graceful shutdown via tokio watch channel
- Settings persisted to app_settings.json alongside existing config files
- StatusBar shows MCP indicator (green/gray dot) with tooltip

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

src/components/layout/Toolbar.tsx

@@ -8,13 +8,15 @@ import { ReadOnlyToggle } from "@/components/layout/ReadOnlyToggle";
 import { useAppStore } from "@/stores/app-store";
 import { useConnections, useReconnect } from "@/hooks/use-connections";
 import { toast } from "sonner";
-import { Database, Plus, RefreshCw, Search } from "lucide-react";
+import { Database, Plus, RefreshCw, Search, Settings } from "lucide-react";
 import type { ConnectionConfig, Tab } from "@/types";
 import { getEnvironment } from "@/lib/environment";
+import { AppSettingsSheet } from "@/components/settings/AppSettingsSheet";
 
 export function Toolbar() {
   const [listOpen, setListOpen] = useState(false);
   const [dialogOpen, setDialogOpen] = useState(false);
+  const [settingsOpen, setSettingsOpen] = useState(false);
   const [editingConn, setEditingConn] = useState<ConnectionConfig | null>(null);
   const { activeConnectionId, currentDatabase, addTab } = useAppStore();
   const { data: connections } = useConnections();
@@ -116,6 +118,16 @@ export function Toolbar() {
         </Button>
 
         <div className="flex-1" />
+
+        <Button
+          variant="ghost"
+          size="sm"
+          className="h-7 w-7 p-0"
+          onClick={() => setSettingsOpen(true)}
+          title="Settings"
+        >
+          <Settings className="h-3.5 w-3.5" />
+        </Button>
       </div>
 
       <ConnectionList
@@ -136,6 +148,11 @@ export function Toolbar() {
         onOpenChange={setDialogOpen}
         connection={editingConn}
       />
+
+      <AppSettingsSheet
+        open={settingsOpen}
+        onOpenChange={setSettingsOpen}
+      />
     </>
   );
 }