fix: show a rate limit message when the GitHub or GitLab API limit is reached - #43

Description

When the unauthenticated GitHub or GitLab API rate limit is reached, the Deploy Repository page now says so instead of showing the generic "GitHub API error." / "GitLab API error.".

A small rateLimitMessage helper treats GitHub's 403 with X-RateLimit-Remaining: 0 and any 429 (GitLab, or GitHub's secondary limit) as a rate limit. It reads X-RateLimit-Reset / RateLimit-Reset (or Retry-After) to show when to try again, for example "GitHub API rate limit reached. Try again after 05:56 PM.", and falls back to "Try again later." when there's no reset header. Both the repository request and the branches request are checked, so a limited branches call no longer quietly turns into an empty branch list. 404 still shows "Repository not found." and other errors keep the existing message.

Notes:

• I didn't add the optional token. A VITE_* variable is compiled into the public bundle, so a GitHub PAT there is visible to anyone who loads the page, and the app doesn't have a GitHub/GitLab OAuth session to reuse. If you want authenticated requests, a FaaS-side proxy seems safer.
• gitlab.com doesn't list RateLimit-Reset in Access-Control-Expose-Headers, so in the browser the GitLab message usually ends with "Try again later." GitHub exposes X-RateLimit-Reset, so the GitHub message shows the time.

Fixes #38

Type of Change

• fix: Bug fix (non-breaking change which fixes an issue)
• feat: New feature (non-breaking change which adds functionality)
• refactor: Code refactor (no functional changes, no API changes)
• docs: Documentation update
• test: Adding or updating tests
• chore: Maintenance (CI, dependencies, tooling)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Screenshots / Recordings

API responses intercepted with a Playwright route (GitHub: 403 + x-ratelimit-remaining: 0, GitLab: 429).

	Before	After
GitHub
GitLab

Checklist

• I have linked the related issue above.
• My code follows the coding standards of this project.
• I have added tests that prove my fix is effective or my feature works.
• New and existing tests pass locally (npm run unit and npm run test).
• My changes generate no new lint warnings or errors (npm run lint).
• My PR title follows Conventional Commits (e.g., fix: resolve login redirect).

npm run unit passes (142 tests, including 5 new ones in deploy_repository_page_test.tsx covering a GitHub 403 limit, a limited branches request, a non-rate-limit 403, a GitLab 429 and a 404). I didn't run the Playwright suite (npm run test). format:check, typecheck and build also pass.