fix: validation error SVG overflow in buildErrorResponse

[jatingow]

Description

Fixes #3467

The 400 and 500 error SVG templates in buildErrorResponse had three problems:

• No viewBox (broken coordinate space)
• No font-size (inherited browser default ~16px, too large)
• No dominant-baseline (text misaligned vertically)
• No truncation (long error messages overflowed the 400×150 box)

Changes

• Added a shared buildInlineErrorSVG() helper with proper viewBox,
  font-size="13", dominant-baseline="central", and 2-line truncation
• Replaced both broken SVG templates with calls to the helper

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

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[github-actions]

⚠️ Hey @jatingow, this PR has merge conflicts with the main branch.

Please pull the latest changes and resolve the conflicts so we can review it!

git fetch origin
git rebase origin/main
# resolve any conflicts, then:
git push --force-with-lease

Once resolved, the needs-rebase label will be removed automatically on the next check. 🙌

[github-actions]

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