Add switch company tool to automation bridge

Summary

The automation bridge (automation-bridge/server.js) currently supports login and template download, but lacks a "switch company" capability. When testing requires a different company (e.g., QBO-connected or sandbox), the user must switch manually in the Excel add-in.

Requested Feature

Add an API endpoint (e.g., POST /api/switch-company) that:

• Accepts a company name or ID
• Triggers the company selector in the add-in to switch to the specified company
• Returns success/failure status

This would enable fully automated test flows that span multiple companies.

Context

• Bridge server: templates-add-in/automation-bridge/server.js
• Bridge client: templates-add-in/src/taskpane/automation/AutomationBridgeClient.ts
• Company selection is currently done via CompanyContext in the React UI