Enhance Error Handling Across ThrottleX

[neelp03]

Description:
Review and enhance error handling across the codebase to ensure all errors are informative and follow Go's best practices (e.g., using errors.Is and errors.As for error wrapping).

Acceptance Criteria:

• Ensure consistent error handling in rate-limiting algorithms and middleware.
• Return informative error messages in cases such as rate limit exceeded, IP extraction failure, etc.
• Add unit tests to validate proper error propagation and error messages.