refactor(svg): extract radar scan line into renderRadarScan() helper (JhaSourav07#2242)

## Description

Fixes JhaSourav07#290

Extracts the animated radar scan `<rect>` element into a
`renderRadarScan(speed, sf, accentColor, autoTheme)` helper.

- Both `renderFooter` (static theme) and `generateAutoThemeSVG` (auto
theme) now call this single helper
- Static theme passes `autoTheme: false` with the resolved accent hex
- Auto theme passes `autoTheme: true` with empty string (uses CSS class)
- Single source of truth for radar scan markup

All 110 existing tests pass.

## Pillar

- [x] 📐 Pillar 2 — Geometric SVG Improvement

## Visual Preview

No visual change — pure refactor. SVG output is identical.

## 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.
- [ ] I have updated `README.md` if I added a new theme or URL
parameter.
- [x] I have starred the repo.
- [x] I have made sure that i have only one commit to merge in this PR.
- [x] The SVG output matches the CommitPulse "premium quality" aesthetic
standard.

Author: JhaSourav07

lib/svg/generator.ts

@@ -488,6 +488,27 @@ function renderTowers(
   return towers;
 }
 
+function renderRadarScan(
+  speed: string,
+  sf: number,
+  accentColor: string,
+  autoTheme: boolean
+): string {
+  const s = createScaler(sf);
+  const fillAttr = autoTheme
+    ? 'class="cp-accent-fill scan-line"'
+    : `fill="${accentColor}" class="cp-accent-fill scan-line"`;
+  return `<rect
+    x="${s(100)}"
+    y="${s(80)}"
+    width="${s(400)}"
+    height="${s(1)}"
+    ${fillAttr}
+    fill-opacity="0.3"
+    style="--scan-speed: ${speed}; --scan-start: ${s(0)}px; --scan-end: ${s(240)}px;"
+  />`;
+}
+
 function renderFooter(
   stats: StreakStats,
   params: BadgeParams,
@@ -500,15 +521,7 @@ function renderFooter(
   return `
   ${!params.hide_stats ? renderStatsSection(stats, labels, s, params) : ''}
   ${!params.hide_title ? `<text x="${s(300)}" y="${s(50)}" text-anchor="middle" class="title">${truncateUsername(safeUser).toUpperCase()}</text>` : ''}
-  <rect
-    x="${s(100)}"
-    y="${s(80)}"
-    width="${s(400)}"
-    height="${s(1)}"
-    class="cp-accent-fill scan-line"
-    fill-opacity="0.3"
-    style="--scan-speed: ${params.speed || '8s'}; --scan-start: ${s(0)}px; --scan-end: ${s(240)}px;"
-  />`;
+  ${renderRadarScan(params.speed || '8s', sf, accent, false)}`;
 }
 
 const MONTH_NAMES = [
@@ -773,22 +786,7 @@ ${
     ? `<text x="${s(300)}" y="${s(50)}" text-anchor="middle" class="title">${truncateUsername(safeUser).toUpperCase()}</text>`
     : ''
 }
-
-  ${
-    animate
-      ? `
-    <rect
-      x="${s(100)}"
-      y="${s(80)}"
-      width="${s(400)}"
-      height="${s(1)}"
-      class="cp-accent-fill scan-line"
-      fill-opacity="0.3"
-      style="--scan-speed: ${params.speed || '8s'}; --scan-start: ${s(0)}px; --scan-end: ${s(240)}px;"
-    />
-    `
-      : ''
-  }
+${renderRadarScan(params.speed || '8s', sf, '', true)}
 </svg>
 `;
 }