feat(classes): weekly recurring schedules with lazy session materialization

class_schedules rules generate concrete session rows for a rolling 28-day
horizon — no cron; materialize runs idempotently on dashboard and public
reads via a partial unique index on (schedule_id, starts_at). Rule delete
stops future sessions; existing sessions keep bookings and overrides.

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

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

apps/backend/internal/api/server.go

@@ -1115,6 +1115,51 @@ func NewServer(cfg config.Config, pools *db.Pools) (*Server, error) {
 		}
 		c.JSON(http.StatusOK, gin.H{"status": "deleted"})
 	})
+	protected.GET("/catalog/class-schedules", func(c *gin.Context) {
+		response, err := catalogService.ListClassSchedules(c.Request.Context(), auth.PrincipalFromContext(c))
+		if err != nil {
+			status := http.StatusInternalServerError
+			if errors.Is(err, catalog.ErrTenantMembership) {
+				status = http.StatusNotFound
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, response)
+	})
+	protected.POST("/catalog/class-schedules", func(c *gin.Context) {
+		var request domain.CreateClassScheduleRequest
+		if err := c.ShouldBindJSON(&request); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid_request"})
+			return
+		}
+		response, err := catalogService.CreateClassSchedule(c.Request.Context(), auth.PrincipalFromContext(c), request)
+		if err != nil {
+			status := http.StatusInternalServerError
+			switch {
+			case errors.Is(err, catalog.ErrTenantMembership), errors.Is(err, catalog.ErrClassTemplateNotFound), errors.Is(err, catalog.ErrLocationNotFound):
+				status = http.StatusNotFound
+			case errors.Is(err, catalog.ErrInvalidInput):
+				status = http.StatusBadRequest
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusCreated, response)
+	})
+	protected.DELETE("/catalog/class-schedules/:scheduleID", func(c *gin.Context) {
+		err := catalogService.DeleteClassSchedule(c.Request.Context(), auth.PrincipalFromContext(c), c.Param("scheduleID"))
+		if err != nil {
+			status := http.StatusInternalServerError
+			switch {
+			case errors.Is(err, catalog.ErrTenantMembership), errors.Is(err, catalog.ErrClassSessionNotFound):
+				status = http.StatusNotFound
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, gin.H{"status": "deleted"})
+	})
 
 	// ============================================
 	// CUSTOMER BOOKING MANAGEMENT API (Public)