fix(kv): Add proper Deno KV client type casting

[felipebarcelospro]

Describe the bug The current implementation uses an unsafe type casting for the Deno KV client, which could lead to type-safety issues and potential runtime errors.

To Reproduce

1. Initialize Drift with Deno KV client in index.ts
2. Current implementation uses unsafe type casting
3. This type casting bypasses TypeScript's type safety
4. Could cause runtime errors if types don't match

Expected behavior Proper type definitions and integration between Deno KV and Drift KV types, ensuring type safety without unsafe casting.

Environment:

• Deno version: 2.0.3
• Drift KV version: latest
• Operating System: Mac OS
• TypeScript version: 5.0+

Additional context The issue can be found in the Drift initialization section of index.ts.

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