feat(classes): session roster + manual waitlist promotion

Adds the roster and manual promotion controls deferred from the booking
lifecycle milestones. Businesses can now inspect who holds a seat and who
is queueing on a class session, and promote waitlisted customers by hand
— including a deliberate over-capacity override when the session is full.

Backend:
- GET /v1/catalog/class-sessions/{id}/roster — session metadata plus
  confirmed and waitlist entry lists with queue positions
- POST /v1/catalog/bookings/{id}/promote — 409 on a full session unless
  allowOverCapacity is set; 400 for non-waitlisted, 404 for missing or
  foreign bookings; reuses the shared confirm path so waitlist ledger
  rows resolve and reminder jobs re-arm
- ListBookingsBySession repository method (pgx + memory); ClassSession
  carries waitlistCount; UpcomingBooking carries classSessionId and
  waitlistPosition
- OpenAPI paths + schemas, regenerated client, catalog service tests

Frontend:
- classes tab session rows expand into a two-column roster panel with
  per-entry promote buttons and an explicit confirm-anyway step on 409
- booking detail modal shows waitlist position and offers promote for
  waitlisted bookings; list badges show #N queue positions
- CS/EN i18n keys and seeded demo roster data; demo mutations surface
  the demo notice

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/frontend/src/components/dashboard/icons.tsx

@@ -96,6 +96,12 @@ export const ChevronRightIcon = () => (
   </svg>
 );
 
+export const ChevronDownIcon = () => (
+  <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+    <path d="m6 9 6 6 6-6"/>
+  </svg>
+);
+
 export const SparklesIcon = () => (
   <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
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