feat(auth): include subscription tier in token and session payload

- Adds subscription tier info to access/refresh tokens.
- Stores tier details in session Redis record.
- Returns tier data in login/register response.
- Uses default tier when user has none.

lib/hooks/use-session-query.ts

@@ -7,6 +7,12 @@ export interface SessionUser {
   username: string;
   email: string;
   characterName: string | null;
+  subscriptionTier: {
+    id: number | null;
+    name: string | null;
+    slug: string | null;
+    level: number | null;
+  } | null;
 }
 
 interface SessionResponse {