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/domain/models.go

@@ -18,18 +18,20 @@ type DashboardKPI struct {
 }
 
 type UpcomingBooking struct {
-	ID            string    `json:"id"`
-	Reference     string    `json:"reference"`
-	CustomerName  string    `json:"customerName"`
-	CustomerEmail string    `json:"customerEmail"`
-	Service       string    `json:"service,omitempty"`
-	Location      string    `json:"location,omitempty"`
-	StaffName     string    `json:"staffName,omitempty"`
-	Notes         string    `json:"notes,omitempty"`
-	StartsAt      time.Time `json:"startsAt"`
-	EndsAt        time.Time `json:"endsAt"`
-	Status        string    `json:"status"`
-	Label         string    `json:"label,omitempty"`
+	ID               string    `json:"id"`
+	Reference        string    `json:"reference"`
+	CustomerName     string    `json:"customerName"`
+	CustomerEmail    string    `json:"customerEmail"`
+	Service          string    `json:"service,omitempty"`
+	Location         string    `json:"location,omitempty"`
+	StaffName        string    `json:"staffName,omitempty"`
+	Notes            string    `json:"notes,omitempty"`
+	StartsAt         time.Time `json:"startsAt"`
+	EndsAt           time.Time `json:"endsAt"`
+	Status           string    `json:"status"`
+	Label            string    `json:"label,omitempty"`
+	ClassSessionID   *string   `json:"classSessionId,omitempty"`
+	WaitlistPosition int       `json:"waitlistPosition,omitempty"`
 }
 
 type WidgetSnippet struct {
@@ -401,6 +403,41 @@ type ClassSession struct {
 	EndsAt       time.Time `json:"endsAt"`
 	Capacity     int       `json:"capacity"`
 	BookedCount  int       `json:"bookedCount"`
+	// WaitlistCount is the number of customers queued for a free seat.
+	WaitlistCount int `json:"waitlistCount"`
+}
+
+// SessionRosterEntry is one booking on a class session roster. WaitlistPosition
+// is the 1-based queue spot for waitlisted entries; zero for confirmed ones.
+type SessionRosterEntry struct {
+	BookingID        string    `json:"bookingId"`
+	Reference        string    `json:"reference"`
+	CustomerName     string    `json:"customerName"`
+	CustomerEmail    string    `json:"customerEmail"`
+	CustomerPhone    string    `json:"customerPhone,omitempty"`
+	Status           string    `json:"status"`
+	WaitlistPosition int       `json:"waitlistPosition,omitempty"`
+	CreatedAt        time.Time `json:"createdAt"`
+}
+
+// SessionRoster is the dashboard attendee view of a class session: confirmed
+// seats plus the waitlist queue in FIFO order.
+type SessionRoster struct {
+	SessionID     string               `json:"sessionId"`
+	TemplateTitle string               `json:"templateTitle"`
+	LocationName  string               `json:"locationName,omitempty"`
+	StartsAt      time.Time            `json:"startsAt"`
+	EndsAt        time.Time            `json:"endsAt"`
+	Capacity      int                  `json:"capacity"`
+	Confirmed     []SessionRosterEntry `json:"confirmed"`
+	Waitlist      []SessionRosterEntry `json:"waitlist"`
+}
+
+// PromoteBookingRequest controls manual waitlist promotion. AllowOverCapacity
+// lets a business deliberately overbook a session; without it the request fails
+// when no free seat remains.
+type PromoteBookingRequest struct {
+	AllowOverCapacity bool `json:"allowOverCapacity,omitempty"`
 }
 
 type CreateClassSessionRequest struct {