feat: implement concurrent GET request deduplication in apiClient using a cache-based coalescing strategy.

[Niffy03]

Description

Coalesces duplicate in-flight GET requests onto a single in-flight promise and fans out the resolved results or errors to all concurrent callers.

Key changes:

• Integrated in-flight request deduplication into apiClient.get() in src/lib/api.ts using dedupe() from src/lib/api/dedupe.ts.
• Added a dedupe?: boolean option to RequestConfig to allow opting out when necessary ({ dedupe: false }).
• Updated cache eviction in dedupe() to ensure completed requests are evicted immediately prior to resolution, allowing immediate subsequent requests to make fresh network calls.
• Added comprehensive unit and integration tests in src/lib/api/__tests__/dedupe.test.ts and src/lib/api/__tests__/api.dedupe.test.ts.

Related Issue

Closes #1160

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Checklist

• Code follows project style guidelines
• Self-review completed
• No console errors
• Uses Lucide icons consistently
• Responsive design implemented
• Starknet best practices followed

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