feat(reports): capacity-based utilization + report CSVs

Utilization now measures booked minutes against each member's
availability-rule capacity in the tenant timezone, replacing the
confirmed-share proxy. StaffMetric exposes booked/capacity minutes.

New endpoints: GET /v1/export/staff-report.csv (reuses StaffMetrics)
and GET /v1/export/service-report.csv (per-service bookings/cancelled/
revenue, class bookings rolled up). Export buttons on the staff
performance panel and services page.

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

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

apps/backend/openapi/bookra.openapi.yaml

@@ -1531,6 +1531,60 @@ paths:
                 type: string
         "404":
           description: Tenant membership not found
+  /v1/export/staff-report.csv:
+    get:
+      tags: [Export]
+      operationId: exportStaffReportCsv
+      security:
+        - bearerAuth: []
+      summary: Export per-staff performance report as CSV
+      description: >-
+        Summarized per-staff metrics — bookings, completed, cancelled, booked
+        and capacity minutes, capacity-based utilization, revenue — over a
+        trailing window. Same aggregation as `GET /v1/metrics/staff`.
+      parameters:
+        - name: days
+          in: query
+          schema:
+            type: integer
+            default: 30
+            maximum: 365
+      responses:
+        "200":
+          description: CSV file download
+          content:
+            text/csv:
+              schema:
+                type: string
+        "404":
+          description: Tenant membership not found
+  /v1/export/service-report.csv:
+    get:
+      tags: [Export]
+      operationId: exportServiceReportCsv
+      security:
+        - bearerAuth: []
+      summary: Export per-service booking report as CSV
+      description: >-
+        Bookings, cancellations, and revenue aggregated per catalog service
+        over a trailing window. Class bookings roll into a final
+        "class sessions" row when present.
+      parameters:
+        - name: days
+          in: query
+          schema:
+            type: integer
+            default: 30
+            maximum: 365
+      responses:
+        "200":
+          description: CSV file download
+          content:
+            text/csv:
+              schema:
+                type: string
+        "404":
+          description: Tenant membership not found
   /v1/public/calendar/{token}:
     get:
       tags: [Calendar]
@@ -2219,7 +2273,7 @@ components:
           description: Caller's read cursor; absent until the first mark-read
     StaffMetric:
       type: object
-      required: [staffId, displayName, bookings, completed, cancelled, utilizationPercent, revenueCents]
+      required: [staffId, displayName, bookings, completed, cancelled, bookedMinutes, capacityMinutes, utilizationPercent, revenueCents]
       properties:
         staffId:
           type: string
@@ -2232,9 +2286,15 @@ components:
           type: integer
         cancelled:
           type: integer
+        bookedMinutes:
+          type: integer
+          description: Sum of non-cancelled booking durations in the window
+        capacityMinutes:
+          type: integer
+          description: Sum of the member's availability-rule minutes across the window, evaluated on local dates in the tenant timezone
         utilizationPercent:
           type: integer
-          description: Share of bookings that stayed confirmed, 0-100
+          description: bookedMinutes / capacityMinutes as a percentage; 0 when the member has no availability rules
         revenueCents:
           type: integer
           format: int64