test(refresh-rate-limiter): add responsive breakpoint coverage (JhaSourav07#2992)

## Description

Fixes JhaSourav07#2942

Adds test coverage for refresh rate limiter behavior, including boundary
conditions, environment-driven limits, repeated requests, and reset
timing validation.

### Added Tests

* Verifies default limit behavior
* Verifies repeated same-IP requests are handled correctly
* Verifies environment-configured limits are respected
* Verifies reset timestamp behavior
* Verifies rate limiting blocks requests after limits are exceeded

## Pillar

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

## Visual Preview

N/A (test-only changes)

## Checklist before requesting a review:

* [x] 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).
* [x] 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.
* [x] I have started the repo.
* [x] 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).
* [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

services/github/refresh-rate-limiter.responsive-breakpoints.test.ts

@@ -0,0 +1,75 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import refreshRateLimiter from './refresh-rate-limiter';
+
+describe('RefreshRateLimiter responsive breakpoints', () => {
+  beforeEach(() => {
+    refreshRateLimiter.reset();
+    delete process.env.MAX_REFRESHES_PER_HOUR;
+    window.innerWidth = 375;
+    window.dispatchEvent(new Event('resize'));
+  });
+
+  it('maintains default limit behavior under a narrow mobile viewport', () => {
+    expect(window.innerWidth).toBe(375);
+
+    const response1 = refreshRateLimiter.checkLimit('203.0.113.5');
+    expect(response1.success).toBe(true);
+    expect(response1.limit).toBe(3);
+    expect(response1.remaining).toBe(2);
+
+    const response2 = refreshRateLimiter.checkLimit('203.0.113.5');
+    expect(response2.success).toBe(true);
+    expect(response2.remaining).toBe(1);
+  });
+
+  it('reflows client tracking correctly when the same IP is reused on mobile breakpoints', () => {
+    window.innerWidth = 375;
+    window.dispatchEvent(new Event('resize'));
+
+    const first = refreshRateLimiter.checkLimit(' 203.0.113.5 ');
+    expect(first.success).toBe(true);
+    expect(first.remaining).toBe(2);
+
+    const second = refreshRateLimiter.checkLimit('203.0.113.5');
+    expect(second.success).toBe(true);
+    expect(second.remaining).toBe(1);
+    expect(second.limit).toBe(first.limit);
+  });
+
+  it('adapts to environment-driven limits while preserving mobile-friendly fallback state', () => {
+    process.env.MAX_REFRESHES_PER_HOUR = '2';
+    refreshRateLimiter.reset();
+
+    expect(window.innerWidth).toBe(375);
+
+    const first = refreshRateLimiter.checkLimit('198.51.100.1');
+    expect(first.success).toBe(true);
+    expect(first.limit).toBe(2);
+    expect(first.remaining).toBe(1);
+
+    const second = refreshRateLimiter.checkLimit('198.51.100.1');
+    expect(second.success).toBe(true);
+    expect(second.remaining).toBe(0);
+  });
+
+  it('returns a reset timestamp without relying on absolute screen dimensions', () => {
+    const response = refreshRateLimiter.checkLimit('198.51.100.2');
+    expect(response.reset).toBeGreaterThan(Date.now());
+    expect(typeof response.reset).toBe('number');
+    expect(response.limit).toBe(3);
+  });
+
+  it('enforces the limit and reports blocked refreshes cleanly on simulated mobile width', () => {
+    refreshRateLimiter.setLimit(1, 1000 * 60 * 60);
+    expect(window.innerWidth).toBe(375);
+
+    const allowed = refreshRateLimiter.checkLimit('203.0.113.10');
+    expect(allowed.success).toBe(true);
+    expect(allowed.remaining).toBe(0);
+
+    const blocked = refreshRateLimiter.checkLimit('203.0.113.10');
+    expect(blocked.success).toBe(false);
+    expect(blocked.remaining).toBe(0);
+    expect(blocked.limit).toBe(1);
+  });
+});