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/backend/internal/catalog/service_test.go

@@ -641,6 +641,123 @@ func TestCancelBookingPromotesWaitlist(t *testing.T) {
 	}
 }
 
+func TestListSessionRoster(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	svc := newCatalogService(repo)
+	ctx := context.Background()
+
+	for i := 0; i < 4; i++ {
+		bookClass(t, repo, fmt.Sprintf("seat%[email protected]", i))
+	}
+	bookClass(t, repo, "[email protected]")
+	bookClass(t, repo, "[email protected]")
+
+	roster, err := svc.ListSessionRoster(ctx, owner, demoSessionID)
+	if err != nil {
+		t.Fatalf("roster: %v", err)
+	}
+	if roster.Capacity != 4 || len(roster.Confirmed) != 4 || len(roster.Waitlist) != 2 {
+		t.Fatalf("unexpected roster %+v", roster)
+	}
+	if roster.Waitlist[0].CustomerEmail != "[email protected]" || roster.Waitlist[0].WaitlistPosition != 1 {
+		t.Fatalf("expected first waiter at position 1, got %+v", roster.Waitlist[0])
+	}
+	if roster.Waitlist[1].WaitlistPosition != 2 {
+		t.Fatalf("expected second waiter at position 2, got %+v", roster.Waitlist[1])
+	}
+	if roster.TemplateTitle != "Small group mobility class" || roster.LocationName != "Main Studio" {
+		t.Fatalf("unexpected roster header %+v", roster)
+	}
+
+	sessions, _ := svc.ListClassSessions(ctx, owner)
+	if sessions[0].WaitlistCount != 2 {
+		t.Fatalf("expected waitlistCount 2, got %d", sessions[0].WaitlistCount)
+	}
+
+	stranger := domain.Principal{Subject: "someone-else", Role: "staff"}
+	if _, err := svc.ListSessionRoster(ctx, stranger, demoSessionID); !errors.Is(err, ErrTenantMembership) {
+		t.Fatalf("expected ErrTenantMembership, got %v", err)
+	}
+	if _, err := svc.ListSessionRoster(ctx, owner, "00000000-0000-0000-0000-000000000099"); !errors.Is(err, ErrClassSessionNotFound) {
+		t.Fatalf("expected ErrClassSessionNotFound, got %v", err)
+	}
+}
+
+func TestPromoteBooking(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	svc := newCatalogService(repo)
+	ctx := context.Background()
+
+	for i := 0; i < 4; i++ {
+		bookClass(t, repo, fmt.Sprintf("seat%[email protected]", i))
+	}
+	first := bookClass(t, repo, "[email protected]")
+	second := bookClass(t, repo, "[email protected]")
+
+	// Full session: strict promote is rejected with ErrSessionFull.
+	if err := svc.PromoteBooking(ctx, owner, second.BookingID, domain.PromoteBookingRequest{}); !errors.Is(err, bookings.ErrSessionFull) {
+		t.Fatalf("expected ErrSessionFull, got %v", err)
+	}
+
+	// The explicit override confirms anyway — deliberate out-of-order
+	// overbooking, skipping the first waiter.
+	if err := svc.PromoteBooking(ctx, owner, second.BookingID, domain.PromoteBookingRequest{AllowOverCapacity: true}); err != nil {
+		t.Fatalf("over-capacity promote: %v", err)
+	}
+	booking, _ := repo.GetBookingByID(ctx, second.BookingID)
+	if booking.Status != "confirmed" {
+		t.Fatalf("expected confirmed after override, got %q", booking.Status)
+	}
+
+	// Confirmed bookings, unknown IDs, and foreign principals are rejected.
+	if err := svc.PromoteBooking(ctx, owner, second.BookingID, domain.PromoteBookingRequest{}); !errors.Is(err, bookings.ErrNotWaitlisted) {
+		t.Fatalf("expected ErrNotWaitlisted for confirmed booking, got %v", err)
+	}
+	if err := svc.PromoteBooking(ctx, owner, "00000000-0000-0000-0000-000000000099", domain.PromoteBookingRequest{}); !errors.Is(err, ErrBookingNotFound) {
+		t.Fatalf("expected ErrBookingNotFound, got %v", err)
+	}
+	stranger := domain.Principal{Subject: "someone-else", Role: "staff"}
+	if err := svc.PromoteBooking(ctx, stranger, first.BookingID, domain.PromoteBookingRequest{}); !errors.Is(err, ErrTenantMembership) {
+		t.Fatalf("expected ErrTenantMembership, got %v", err)
+	}
+}
+
+func TestPromoteBookingWithFreeSeat(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	svc := newCatalogService(repo)
+	ctx := context.Background()
+
+	// A waitlisted booking on a session with free capacity — an edge state the
+	// auto-promoter cannot reach, e.g. a queue entry left after manual edits.
+	session, err := repo.GetClassSessionByID(ctx, demoSessionID)
+	if err != nil {
+		t.Fatalf("get session: %v", err)
+	}
+	created, err := repo.CreateBooking(ctx, db.CreateBookingParams{
+		TenantID:       "5d6b3551-0a3e-4b86-bdf0-e9df20a47148",
+		ClassSessionID: &[]string{demoSessionID}[0],
+		BookingMode:    "class",
+		CustomerName:   "Queued Customer",
+		CustomerEmail:  "[email protected]",
+		StartsAt:       session.StartsAt,
+		EndsAt:         session.EndsAt,
+		Status:         "waitlisted",
+		Reference:      "BOK-QUEUED",
+		ManageToken:    "queued-token",
+	})
+	if err != nil {
+		t.Fatalf("seed waitlisted booking: %v", err)
+	}
+
+	if err := svc.PromoteBooking(ctx, owner, created.ID, domain.PromoteBookingRequest{}); err != nil {
+		t.Fatalf("promote with free seat: %v", err)
+	}
+	booking, _ := repo.GetBookingByID(ctx, created.ID)
+	if booking.Status != "confirmed" {
+		t.Fatalf("expected confirmed, got %q", booking.Status)
+	}
+}
+
 func TestUpdateClassTemplate(t *testing.T) {
 	repo := db.NewMemoryRepository()
 	svc := newCatalogService(repo)