docs: create comprehensive README with detailed project information

[xissy]

Summary

• Replace minimal README with comprehensive documentation covering all aspects of the Oh My Zwift app
• Add detailed sections for features, tech stack, installation, development, and contribution guidelines
• Include API endpoints documentation and in-depth feature descriptions

Changes

• Added project overview and purpose
• Listed all key features with descriptions
• Documented complete tech stack
• Created getting started guide with prerequisites
• Added development section with project structure
• Documented all available scripts
• Included API integration details
• Added detailed feature explanations
• Included contributing guidelines and support information

Test plan

• README displays correctly on GitHub
• All commands in the README work as documented
• Links and formatting render properly

🤖 Generated with Claude Code

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	68.57% (-0.41% 🔻)	1163/1696
🟡	Branches	61.38% (-2.76% 🔻)	89/145
🟡	Functions	70.59%	36/51
🟡	Lines	68.57% (-0.41% 🔻)	1163/1696

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟡	libs/zwiftpower.ts	74.07% (-25.93% 🔻)	42.86% (-57.14% 🔻)	100%	74.07% (-25.93% 🔻)

Test suite run success

36 tests passing in 10 suites.

Report generated by 🧪jest coverage report action from 88d7016