Security for group access added succesfully

[Sadeequ]

Closes #92

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closes #92
A new security utility has been created at /workspaces/AnonChat/lib/auth/group-access.ts to serve as a group access validation middleware.

This new file introduces a single function, validateGroupAccess, which is designed to be a reusable component for protecting group-specific API endpoints.

Here’s a breakdown of its functionality:

Dual-Layer Membership Validation: It first checks for direct wallet membership in the group_membership table. If that fails, it provides backward compatibility by checking if the wallet belongs to a user profile that is a member of the group via the room_members table.
Input Sanitization: It validates the roomId and the format of the walletAddress before proceeding.
Standardized Error Responses: It returns structured JSON error responses with appropriate HTTP status codes (400 for bad requests, 403 for unauthorized access, and 500 for server errors).
Security Logging: The middleware includes clear logging for unauthorized access attempts and database errors, which is crucial for auditing and debugging.

This implementation successfully creates a secure and efficient middleware component that aligns with the platform's security guidelines.

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[Sadeequ]

Review my PR and close please.