Gemini enterpise AI integration

[LinceMathew]

Summary

Google Enterprise AI Added to AI Connectors
We've added Google Enterprise AI support to git-lrc. Here's the how-to guide:

Setup Steps

1. From the git-lrc UI, select the Gemini Enterprise option.
2. Generate and download a service account JSON file from the Google Cloud Console. Learn how
3. Upload the service account JSON file, add your project ID, and specify the project region.
4. Select your preferred Gemini model, validate the configuration, and save.

Screenshot

Linked Issue

Link the agreed issue this PR fulfills.

Validation

Ran headless-safe Node.js unit tests locally:

make test-js

All 34 tests passed successfully.

Checklist

• This PR fulfills an agreed issue.
• I kept the change narrow and scoped.
• I ran the most specific relevant validation and described it above.
• If I changed behavior, I called that out clearly in this PR.
• If I touched UI, I attached a GIF or video walkthrough. This is required.
• If I changed storage/ responsibilities, I updated storage/storage_status.md and ran make check-status-doc.
• If I changed network/ responsibilities, I updated network/network_status.md and ran make check-status-doc.
• If this change touches security, disclosure flow, credentials, storage, network behavior, or remote data handling, I reviewed SECURITY.md and updated related documentation if needed.

Notes For Reviewers

Anything specific you want reviewers to focus on.