feat(rln): implement UI & UX enhancements, clean up package

[danisharora099]

Description

The Web Dapp should have a clean, intuitive UI with clear error messages and helpful tooltips.

User Story

• As a user, I want an easy-to-use interface with explanations, so that I can manage my RLN membership without confusion.
• As a user, I want to receive clear error messages, so that I can troubleshoot issues.

Proposed Solution / Feature Design

• Improve the UI layout with TailwindCSS (or another UI framework).
• Add tooltips for RLN membership parameters (rate limits, expiration).
• Display error messages in a user-friendly manner.
• Implement a dark mode toggle (if needed).

Optional: Diagram or Draft of Design

Notes