Documentation — AI features guide and API docs update

[anurag629]

Documentation for AI Features

Update all relevant documentation to cover the new AI capabilities.

Scope

API Docs Page (`/api-docs`)

Add a new section documenting the AI endpoints:

• `POST /api/ai/validate` — request/response format, supported providers
• `POST /api/ai/generate` — request/response format, parameters
• `POST /api/ai/autofill` — request/response format
• Note that these endpoints require users to pass their own API key (BYOK)
• Security note: keys are proxied, never stored

Homepage / Features Section

• Update the features grid or add a new section highlighting AI capabilities
• Keep it subtle — AI is a power feature, not the primary value prop

README.md

• Add "AI Features" section explaining BYOK model
• List supported providers
• Quick setup instructions (get API key → paste in settings → use)

CLAUDE.md

• Add AI-related file paths and architecture notes
• Document the provider registry pattern
• Note the proxy endpoint pattern

In-App Help

• Tooltips on AI buttons explaining what they do
• "Learn more" links in the AI Settings modal
• First-time AI usage: brief inline explainer

Acceptance Criteria

• API docs page covers all AI endpoints with examples
• README includes AI features section
• CLAUDE.md updated with AI architecture
• In-app tooltips and help text are clear
• No broken links
• Screenshots/mockups updated if applicable