docs: remove outdated API references from README

[1234-ad]

Remove Outdated API References from README

This PR cleans up the README by removing references to the API package that was removed in recent commits.

Changes Made

• Removed API Environment Variables Section: Eliminated the entire API (apps/api/.env.example) section since the API package no longer exists
• Updated Documentation: Kept only the relevant Web app environment variables
• Maintained Structure: Preserved all other sections and formatting

Context

Based on recent commits (SHA: 54a3abd and d01119b), the API package was removed from the monorepo. However, the README still contained detailed documentation about API environment variables that are no longer relevant.

Impact

• ✅ Documentation Accuracy: README now reflects the current codebase structure
• ✅ Developer Experience: Eliminates confusion about non-existent API configuration
• ✅ Maintenance: Keeps documentation in sync with code changes
• ✅ No Breaking Changes: Only removes outdated information

This is a simple documentation cleanup that ensures new contributors aren't confused by references to removed components.

[Sanurags219]

Maintained Structure: Preserved all other sections and formatting