fix(a11y): update aria labels for social links (JhaSourav07#3000)

## Description

Fixes JhaSourav07#2949

Adds responsive breakpoint-focused test coverage for the refresh rate
limiter utility.

### Added Tests

* Verifies default limit behavior under mobile-width simulation
* Verifies repeated same-IP requests are handled consistently
* Verifies environment-driven limits under narrow viewport conditions
* Verifies reset timestamp behavior
* Verifies limit enforcement when thresholds 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.
* [ ] 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.
* [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

components/ShareButtons.tsx

@@ -19,12 +19,16 @@ export default function ShareButtons({ url, title = '' }: ShareButtonsProps) {
         href={linkedinUrl}
         target="_blank"
         rel="noopener noreferrer"
-        aria-label="Share on LinkedIn"
+        aria-label="Share on LinkedIn (opens in a new tab)"
       >
         <FaLinkedin size={24} aria-hidden="true" />
       </a>
-
-      <a href={twitterUrl} target="_blank" rel="noopener noreferrer" aria-label="Share on X">
+      <a
+        href={twitterUrl}
+        target="_blank"
+        rel="noopener noreferrer"
+        aria-label="Share on X / Twitter (opens in a new tab)"
+      >
         <FaXTwitter size={24} aria-hidden="true" />
       </a>
     </div>