docs: consolidate frontend documentation into single FRONTEND.md

[zinodict121]

docs: consolidate frontend documentation into single FRONTEND.md

Closes #182

Description

This PR consolidates the previously fragmented frontend documentation files into a single, cohesive source of truth (FRONTEND.md). This change improves discoverability for developers and ensures all frontend guidelines (like accessibility and component structures) are centralized.

Changes Made

• Created a comprehensive FRONTEND.md that acts as the primary source for all frontend documentation.
• Merged the contents of docs/ACCESSIBILITY.md and src/accessibility/audit-report.md into FRONTEND.md.
• Added placeholder sections for future Component Library and Styling Guide documentation.
• Replaced the repository README.md with a minimal stub that directly links to FRONTEND.md, maintaining open-source repository landing page best practices while enforcing the single source of truth.
• Removed the old, obsolete markdown files to prevent fragmentation and confusion.

Testing

• Verified that markdown formatting, code blocks, and tables from all merged documents render correctly in FRONTEND.md.
• Verified that README.md acts as a functional pointer.
• Ensured no broken links remain from the removed files.