feat: Upgrade QA chat to latest Gemini models + add Claude support

[louis030195]

Overview

Update the Execution QA Chat AI model options to include the latest Gemini models and add Claude as an alternative provider.

Current State

• File: src/components/deployments/ExecutionAIChat.tsx:253-260
• Models: gemini-2.5-pro, gemini-2.5-flash
• Backend: src/lib/vertexai.ts already supports Gemini 3 via gemini-3-pro-preview

Tasks

1. Add Gemini 3 to QA chat model selector

The model mapping already exists in vertexai.ts:280-281:

'gemini-3-pro': 'gemini-3-pro-preview',
'gemini-3-pro-preview': 'gemini-3-pro-preview',

Just need to add it to the dropdown in ExecutionAIChat.tsx.

2. Consider adding Claude support

Options:

• Add Anthropic API integration for Claude models
• Models to consider: claude-sonnet-4-5, claude-3-5-haiku
• Would require new API route or modification to existing /api/ai/execution-qa

Acceptance Criteria

• Gemini 3 Pro available in QA chat model selector
• (Optional) Claude models available as alternative
• Model selection persists across sessions (localStorage)
• Works with existing conversation history

Notes

• Gemini 3 requires global location endpoint (already handled in vertexai.ts:460-461)
• Claude would need ANTHROPIC_API_KEY env var in Vercel