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/ipc/ipc_client.ts

@@ -68,6 +68,7 @@ import type {
   CloneRepoParams,
   SupabaseBranch,
   SetSupabaseAppProjectParams,
+  SelectNodeFolderResult,
 } from "./ipc_types";
 import type { Template } from "../shared/templates";
 import type {
@@ -1180,6 +1181,16 @@ export class IpcClient {
     return this.ipcRenderer.invoke("select-app-folder");
   }
 
+  // Add these methods to IpcClient class
+
+  public async selectNodeFolder(): Promise<SelectNodeFolderResult> {
+    return this.ipcRenderer.invoke("select-node-folder");
+  }
+
+  public async getNodePath(): Promise<string | null> {
+    return this.ipcRenderer.invoke("get-node-path");
+  }
+
   public async checkAiRules(params: {
     path: string;
   }): Promise<{ exists: boolean }> {