docs: entire docs revamp

[Pratham-Mishra04]

Summary

Restructured the documentation architecture to improve organization and navigation. Created a new documentation structure with dedicated sections for features, integrations, architecture, and more.

Changes

• Completely reorganized the documentation folder structure
• Created new sections for Go SDK, features, integrations, and architecture
• Added detailed Go SDK documentation including multimodal, streaming, and tool calling
• Moved old documentation to an old-docs folder for reference
• Updated docs.json with the new navigation structure

Type of change

• Bug fix
• Feature
• Refactor
• Documentation
• Chore/CI

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (Next.js)
• Docs

How to test

The documentation can be tested by running the documentation site locally:

# Install mintlify if needed
npm install -g mintlify

# Run the docs site
mintlify dev

Navigate through the new structure to ensure all links work correctly.

Breaking changes

• Yes
• No

Related issues

Improves documentation organization as discussed in team meetings.

Security considerations

No security implications.

Checklist

• I read docs/contributing/README.md and followed the guidelines
• I added/updated tests where appropriate
• I updated documentation where needed
• I verified builds succeed (Go and UI)
• I verified the CI pipeline passes locally if applicable