feat: allow manual Node.js path configuration (#1577)

Add ability to manually configure Node.js path for users who have
Node.js
installed but not in their system PATH.

Features:
- Browse and select custom Node.js installation folder
- Visual status indicator showing Node.js version or "Not found"
- Reset to system default PATH option
- Manual configuration option in setup banner
- Real-time Node.js status checking

closes #1050

    
<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Adds manual Node.js path configuration so the app works even when Node
isn’t on PATH, fulfilling #1050. Users can browse to their install,
reset to default, and see real-time status in Settings and during setup.

- New Features
- Settings: NodePathSelector to browse a Node.js folder, show
version/“Not found” status, and reset to system PATH (persists
customNodePath).
- Setup banner: manual config flow with a folder picker if Node is
already installed.
- IPC: select-node-folder, set-node-path, get-node-path; reloads env and
prepends custom path to PATH.
- Real-time Node.js status check with visual indicator (CheckCircle on
valid).
  - E2E tests for browse, reset, and valid-status display.

<!-- End of auto-generated description by cubic. -->

src/pages/settings.tsx

@@ -24,6 +24,7 @@ import { AutoUpdateSwitch } from "@/components/AutoUpdateSwitch";
 import { ReleaseChannelSelector } from "@/components/ReleaseChannelSelector";
 import { NeonIntegration } from "@/components/NeonIntegration";
 import { RuntimeModeSelector } from "@/components/RuntimeModeSelector";
+import { NodePathSelector } from "@/components/NodePathSelector";
 import { ToolsMcpSettings } from "@/components/settings/ToolsMcpSettings";
 
 export default function SettingsPage() {
@@ -272,6 +273,9 @@ export function GeneralSettings({ appVersion }: { appVersion: string | null }) {
       <div className="mt-4">
         <RuntimeModeSelector />
       </div>
+      <div className="mt-4">
+        <NodePathSelector />
+      </div>
 
       <div className="flex items-center text-sm text-gray-500 dark:text-gray-400 mt-4">
         <span className="mr-2 font-medium">App Version:</span>