Enhance Contribution Endpoint with Rate Limiting and Token Support

[Rakshak05]

Description

Fixes #8572

Adds per-IP rate limiting (10 req/min) on contribution data requests, creates the /api/contributions endpoint, supports caller-supplied GitHub tokens (Authorization: Bearer <token>, x-github-token, or ?token=) for high-volume usage, and attaches standard Retry-After & X-RateLimit-* headers to HTTP 429 rate-limited responses.

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

N/A (Backend API rate-limiting & endpoint resilience fix)

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 starred 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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[retenta-bot]

This pull request adds important features to the contribution endpoint, including rate limiting and support for caller tokens, which aligns with our previous decisions on handling API rate limits effectively. For instance, the implementation of rate limit handling in the /api/streak endpoint has set a precedent for improving user experience during rate limit exhaustion. Additionally, the focus on security in past decisions, such as sanitizing error responses, complements this enhancement. Thank you for your contributions, and I look forward to your updates!

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

Asset	PR Size	Base Size	Difference	Status
static/chunks/app/api/contributions/route-[hash].js	0.29 KB	-	+0.29 KB (++100%)	🆕 New
static/chunks/main-[hash].js	41.29 KB	41.28 KB	+0.01 KB (+0.03%)	🔴 Regression

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	5005.33 KB	5004.32 KB	+1.02 KB (+0.02%)
Total CSS	354.80 KB	354.80 KB	0 B

[Aamod007]

Great job implementing the new /api/contributions\ endpoint! The addition of per-IP rate limiting and custom token support is an excellent architectural improvement for scalability and abuse prevention. The tests are solid. Approved!