Improve mobile responsiveness

[rafactx]

Mobile Responsiveness Audit

Perform a full review of the documentation site across common mobile breakpoints (<768px).
The goal is to ensure consistent layout, proper scaling of components, and smooth navigation without visual glitches or overlapping elements.

Acceptance Criteria

• No horizontal scrolling on any page
• Navigation and sidebar adapt correctly to small screens
• Code blocks and API reference remain readable
• Hero and cards scale without distortion