Temi/Kyle: Subscription Logic & UI Integration

[kn-dev-code]

Context: Your goal is to move the "Plan: Pro" badge from a static design to a dynamic state.

Feature Logic: Create a useSubscription hook or add an action to useAuth that sends a PATCH request to /user/upgrade.

UI Work: * Update the NavBar to conditionally render the "Plan: Pro" badge based on user.plan === 'pro'.

Fix the TypeScript error in the NavBar: The user object is currently typed as a string, but we need it to be an object so we can access {user.name} without it crashing.

Deliverable: A functional "Upgrade" button that changes the user's plan in the database and reflects immediately in the UI.

[kn-dev-code]

Performed a full refactor of the subscription logic. Key fixes included:

Implementing the useSubscription hook for dynamic 'Plan: Pro' badge rendering.

Fixing the TypeScript error in the NavBar where the user object was incorrectly typed as a string.

Integrating the PATCH request to /user/upgrade to ensure the database and UI stay in sync.