Make reverse proxy documentation more beginner-friendly

[deluan]

This PR improves the reverse proxy documentation to make it more accessible for beginners. Changes include:

• Added a clear introduction explaining what reverse proxy authentication is and its benefits
• Created a Quick Start section for users to get the basic idea before diving into details
• Restructured the content flow from simple to complex concepts
• Enhanced explanations with more context and simpler language
• Added visual elements including a simple diagram and formatted examples
• Improved formatting with better section headers, alerts, and code examples
• Added troubleshooting and FAQ sections to address common issues

[deluan]

Hey @crazygolem, I did a cleanup in the Reverse Proxy page. Can you give it a quick review and let me know what do you think? Thanks!