feat: scheduled report digests + per-session capacity (M33)

POST /v1/internal/jobs/reports/dispatch emails each tenant owner a
trailing-window digest (bookings, revenue, per-service and per-staff
breakdown) localized to the tenant locale; zero-activity tenants are
skipped. Metrics cores extracted to tenant-scoped variants so the job
needs no principal.

PATCH /v1/catalog/class-sessions/:id sets a session's seat count with
a confirmed-bookings floor — shrinking below it needs allowOverCapacity,
matching the waitlist-promotion convention. Session rows gain an inline
capacity editor with an overbook confirm state.

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

apps/backend/internal/domain/models.go

@@ -263,6 +263,15 @@ type DispatchReminderJobsResponse struct {
 	SkippedCount   int `json:"skippedCount"`
 }
 
+// DispatchReportDigestsResponse summarizes one run of the scheduled digest
+// job: how many tenants were considered and how the sends resolved.
+type DispatchReportDigestsResponse struct {
+	TenantCount  int `json:"tenantCount"`
+	SentCount    int `json:"sentCount"`
+	SkippedCount int `json:"skippedCount"`
+	FailedCount  int `json:"failedCount"`
+}
+
 // ============================================
 // LOCATION / ZONE MODELS
 // ============================================
@@ -470,6 +479,14 @@ type CreateClassSessionRequest struct {
 	Capacity   *int    `json:"capacity,omitempty"`
 }
 
+// UpdateClassSessionRequest patches a single session. Capacity is the only
+// staff-editable field; shrinking below the confirmed seat count needs
+// AllowOverCapacity (same convention as promoting onto a full session).
+type UpdateClassSessionRequest struct {
+	Capacity          *int `json:"capacity"`
+	AllowOverCapacity bool `json:"allowOverCapacity,omitempty"`
+}
+
 // ClassSchedule is a weekly recurring rule for a class template. Concrete
 // sessions are materialized for a rolling horizon; DayOfWeek follows Go's
 // time.Weekday (Sunday=0) and StartsLocal is an "HH:MM" tenant-local time.