test(themes): verify THEME_KEYS matches themes object (JhaSourav07#832)

## Description

Fixes JhaSourav07#665 

Added a Vitest suite to `app/customize/types.test.ts` to ensure
`THEME_KEYS` stays perfectly synchronized with `lib/svg/themes.ts`. It
also verifies the presence of the default `auto` and `random` states.

## Pillar

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

## Visual Preview
<img width="1365" height="767" alt="Screenshot 2026-05-28 090702"
src="https://github.com/user-attachments/assets/849b984f-45ff-4b55-a594-cbfa953bb1d2"
/>

## 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): ...`).
- [x] 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.
- [x] The SVG output matches the CommitPulse "premium quality" aesthetic
standard.

Author: JhaSourav07

app/customize/types.test.ts

@@ -0,0 +1,17 @@
+import { describe, it, expect } from 'vitest';
+import { THEME_KEYS } from './types';
+import { themes } from '../../lib/svg/themes';
+
+describe('Theme Keys Synchronization', () => {
+  it('THEME_KEYS should exactly match the themes object keys plus "auto" and "random"', () => {
+    // 1. Create the exact array of what should exist
+    const expectedKeys = ['auto', ...Object.keys(themes), 'random'];
+
+    // 2. Sort both arrays alphabetically so the test doesn't fail just because of order
+    const sortedExpected = expectedKeys.sort();
+    const sortedActual = [...THEME_KEYS].sort();
+
+    // 3. Assert they are 100% identical (no missing keys, no extra obsolete keys)
+    expect(sortedActual).toEqual(sortedExpected);
+  });
+});