fix: filter dashboard role cards by registered role

[EmeditWeb]

Problem

Dashboard.tsx shows Sponsor, Vendor, and Mentor role cards to every user regardless of whether they have registered for that role. A user who is only a sponsor sees vendor and mentor options.

What To Build

1. Add API call to check which roles the current wallet has registered
2. Show only registered role cards (or role selector if not yet registered)
3. Add loading state while checking registered roles

Files To Touch

• src/pages/Dashboard.tsx

Acceptance Criteria

• Only registered role cards shown
• Unregistered users see role selector
• Loading state while checking
• Build passes

Mandatory Checks

• context/ files read
• npm run build passes
• PR references this issue