Feat: Add welcome modal functionality for user onboarding

[MathisVerstrepen]

Short Summary

This PR introduces an onboarding flow for users who have not yet configured their OpenRouter API key. It adds a persistent "Welcome" state to the user profile and implements a modal on the home dashboard that prompts users to set up their API credentials, ensuring the application is usable immediately after signup.

Technical Changes

Database & Backend (api/)

• Schema Update: Added has_seen_welcome (boolean, default False) to the User SQLModel and associated Alembic migration (b6ac4c311f9d).
• API Endpoints:
  • Added POST /user/ack-welcome in routers/users.py to allow the frontend to mark the onboarding as complete.
  • Updated sync_user and UserRead models to return the has_seen_welcome status.
• CRUD Operations: Implemented mark_user_as_welcomed in user_crud.py.

Frontend (ui/)

• New Component: Created components/ui/home/welcomeModal.vue, a styled modal featuring animations and a direct link to settings.
• Page Logic (pages/index.vue):
  • Added a watcher on isReady state.
  • Logic triggers the modal only if: The user has not seen the welcome screen AND the user has no OpenRouter API key configured in Pinia.
• Server Middleware:
  • Added server/api/auth/ack-welcome.post.ts as a proxy to the backend endpoint, which also refreshes the user session to reflect the state change immediately.
  • Updated github.get.ts, google.get.ts, and login.post.ts to include has_seen_welcome in the session user object.
• Type Definitions: Updated types/user.d.ts to include the new boolean field.

Impact and Scope

• Functional Impact: Users logging in for the first time (or those without API keys who haven't acknowledged the modal) will be interrupted by a welcome modal guiding them to the Settings page.
• System Reach:
  • Database: Requires running Alembic migrations to add the has_seen_welcome column to the users table.
  • Auth: Modifies the session payload structure.
• Breaking Changes: None. The default value for existing users is False, meaning they may see the modal once if they haven't configured an API key, which is intended behavior.
• Performance/Security: Minimal impact. The state check is performed client-side based on session data.