refactor(svg): remove duplicated accessibility metadata in auto theme renderer JhaSourav07#399 (JhaSourav07#624)

## Description

Fixes JhaSourav07#399 
- reused the shared renderHeader() helper inside generateAutoThemeSVG()
- removed duplicated accessibility metadata and defs block
- aligned auto-theme renderer with the latest shared renderer
architecture

Updated this PR to align with the latest upstream renderer refactor,
reusing the new shared `renderHeader()` helper to remove the remaining
duplicated accessibility metadata block.

## Pillar

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

## Visual Preview

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
- [x] 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

lib/svg/generator.ts

@@ -294,13 +294,7 @@ function generateAutoThemeSVG(
   fill="none"
   role="img"
 >
-  <title>CommitPulse Stats for ${safeUser} </title>
-  <desc>
-    ${params.user || 'This user'} has ${stats.totalContributions} total contributions and a longest streak of ${stats.longestStreak} days.
-  </desc>
-  <defs>
-    <filter id="glow" x="-50%" y="-50%" width="200%" height="200%"><feGaussianBlur stdDeviation="${fs(5)}" result="blur" /><feComposite in="SourceGraphic" in2="blur" operator="over" /></filter>
-  </defs>
+  ${renderHeader(safeUser, stats, sf)}
 
   <style>
   @import url('https://fonts.googleapis.com/css2?family=Fira+Code&amp;family=JetBrains+Mono&amp;family=Roboto&amp;display=swap');