test(cache): add unicode and emoji character key handling (JhaSourav07#1990)

## Description

Fixes JhaSourav07#1404 

## Pillar

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

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- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
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resolved all errors (CI will fail otherwise).
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Author: JhaSourav07

lib/cache.test.ts

@@ -578,6 +578,28 @@ describe('TTLCache', () => {
       cache.destroy();
     });
   });
+
+  it('stores and retrieves values with unicode and emoji cache keys', () => {
+    const cache = new TTLCache<string>();
+
+    const unicodeKey = 'cache_🔥_key';
+    const emojiKey = '🚀_rocket_🚀';
+    const mixedKey = 'user_👤_data_🔐';
+
+    cache.set(unicodeKey, 'fire-value', 60_000);
+    cache.set(emojiKey, 'rocket-value', 60_000);
+    cache.set(mixedKey, 'secure-data', 60_000);
+
+    expect(cache.get(unicodeKey)).toBe('fire-value');
+    expect(cache.get(emojiKey)).toBe('rocket-value');
+    expect(cache.get(mixedKey)).toBe('secure-data');
+
+    expect(cache.has(unicodeKey)).toBe(true);
+    expect(cache.has(emojiKey)).toBe(true);
+    expect(cache.has(mixedKey)).toBe(true);
+
+    cache.destroy();
+  });
 });
 
 import { DistributedCache } from './cache';