fix(cache): reject oversized keys to prevent memory bloat JhaSourav07#1403 (JhaSourav07#2040)

## Description

Added strict length validation to the `TTLCache` `set` method to reject
extremely large cache keys (e.g., `'a'.repeat(20000)`). This prevents
potential memory bloat and database strain. Also updated the
corresponding Vitest suite in `lib/cache.test.ts` to assert this new
boundary behavior and removed an older, conflicting test.

Fixes JhaSourav07#1403

## 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 (Backend cache logic update)

## Checklist before requesting a review:

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resolved all errors (CI will fail otherwise).
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`feat(themes): ...`, `fix(calculate): ...`).
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parameter.
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Author: JhaSourav07

lib/cache.test.ts

@@ -673,16 +673,18 @@ describe('TTLCache', () => {
       cache.destroy();
     });
 
-    it('handles oversized cache keys safely', () => {
+    // FIX: New test targeting oversized cache keys for Issue #1403
+    it('rejects oversized cache keys to prevent memory bloat (Variation 2)', () => {
       const cache = new TTLCache<string>();
-
       const oversizedKey = 'a'.repeat(20000);
 
+      // Assert that setting a massive key throws an error to prevent memory bloat
       expect(() => {
         cache.set(oversizedKey, 'large-key-value', 60_000);
-      }).not.toThrow();
+      }).toThrow();
 
-      expect(cache.get(oversizedKey)).toBe('large-key-value');
+      // Verify the key was not saved
+      expect(cache.has(oversizedKey)).toBe(false);
 
       cache.destroy();
     });

lib/cache.ts

@@ -159,6 +159,10 @@ export class TTLCache<T> {
     if (key === '') throw new Error('Cache key cannot be empty');
     if (ttlMs <= 0) throw new RangeError(`ttlMs must be positive, got ${ttlMs}`);
 
+    if (key.length > 10000) {
+      throw new Error('Cache key exceeds maximum allowed length to prevent memory bloat');
+    }
+
     const maxSize = this.maxSize;
     if (maxSize !== undefined && this.store.size >= maxSize && !this.store.has(key)) {
       this.sweep();