feat: data surfacing — intake labels, service metrics, honest capacity

- booking views gain intakeLabels (declared key→label join); dashboard
  modal + manage view render real question labels with slug fallback
- GET /v1/metrics/services aggregates bookings/completed/cancelled/
  revenue per service + classBookings; service-report.csv delegates to
  the same ServiceMetrics aggregation and gains a completed column
- services page gains a Service performance card (per-service stat grid,
  locale CZK revenue, class-bookings footer); demo rows match the
  fabricated service list
- staff capacity utilization subtracts blocked days — tenant-wide and
  staff-scoped blocks remove that day's rule minutes via blockedAt
- tests: blocked-day capacity (tenant + staff scope), service aggregation

Authored By: TDvorak <[email protected]>

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

@@ -1369,6 +1369,20 @@ func NewServer(cfg config.Config, pools *db.Pools) (*Server, error) {
 		c.JSON(http.StatusOK, response)
 	})
 
+	protected.GET("/metrics/services", func(c *gin.Context) {
+		days, _ := strconv.Atoi(c.DefaultQuery("days", "30"))
+		response, err := bookingService.ServiceMetrics(c.Request.Context(), auth.PrincipalFromContext(c), days)
+		if err != nil {
+			status := http.StatusInternalServerError
+			if errors.Is(err, bookings.ErrTenantMembership) {
+				status = http.StatusNotFound
+			}
+			c.JSON(status, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, response)
+	})
+
 	protected.GET("/export/bookings.csv", func(c *gin.Context) {
 		from, to := exportRange(c)
 		var buf bytes.Buffer