feat: Clerk

[danctila]

Description

Add Clerk for authentication across web and mobile clients.

Considerations

Backend

• Sync Clerk user IDs with existing users table
• Verify Clerk JWT tokens in API middleware
• Handle user creation webhook from Clerk -> populate users table with metadata
• Update user model to include external auth ID reference

Web

• Look into @clerk/clerk-react
  • Wrap w/ <ClerkProvider>
• Protect routes
• Add sign-in/up flows

Mobile

• Look into @clerk/clerk-expo
  • Also referenced here in Clerk docs
• Configure Clerk provider in app/_layout.tsx
• Consider OAuth redirects

Shared

• Update API client to attatch Clerk session tokens to requests
• Add auth utilities for token management

DB

• Migration for Clerk user id's