feat: series-aware schedule edits + waitlist ledger removal (M32)

PATCH /v1/catalog/class-schedules/:id patches a recurring rule and,
with applyToFuture, retimes materialized future sessions to the new
local start time on their existing dates — moving confirmed and
waitlisted bookings with them and re-arming reminders. Zones-page
schedule rows gain an inline editor (CS/EN).

Also drops the vestigial waitlist_entries table (migration 00020):
positions derive from bookings.created_at, so the ledger was written
but never read.

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

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

apps/backend/internal/db/class_schedules.go

@@ -99,3 +99,89 @@ func (r *PGRepository) MaterializeScheduleSessions(ctx context.Context, tenantID
 	`, tenantID, now, days)
 	return err
 }
+
+// UpdateClassSchedule edits an existing recurring rule; nil fields are kept.
+// The tenant guard makes the update a no-match error for foreign schedules.
+func (r *PGRepository) UpdateClassSchedule(ctx context.Context, tenantID string, scheduleID string, params UpdateClassScheduleParams) (ClassScheduleRecord, error) {
+	var record ClassScheduleRecord
+	err := r.pool.QueryRow(ctx, `
+		UPDATE class_schedules SET
+			day_of_week = COALESCE($3, day_of_week),
+			starts_local = COALESCE($4::time, starts_local),
+			location_id = CASE WHEN $5::text IS NULL THEN location_id WHEN $5::text = '' THEN NULL ELSE $5::uuid END,
+			active = COALESCE($6, active)
+		WHERE id = $1 AND tenant_id = $2
+		RETURNING `+classScheduleColumns+`
+	`, scheduleID, tenantID, params.DayOfWeek, params.StartsLocal, params.LocationID, params.Active).Scan(
+		&record.ID,
+		&record.TenantID,
+		&record.TemplateID,
+		&record.LocationID,
+		&record.DayOfWeek,
+		&record.StartsLocal,
+		&record.Active,
+		&record.CreatedAt,
+	)
+	return record, err
+}
+
+// ListClassSessionsBySchedule returns materialized sessions of one rule,
+// optionally only those starting after `after`.
+func (r *PGRepository) ListClassSessionsBySchedule(ctx context.Context, tenantID string, scheduleID string, after time.Time) ([]ClassSessionRecord, error) {
+	rows, err := r.pool.Query(ctx, `
+		SELECT `+classSessionColumns+`
+		FROM class_sessions cs
+		INNER JOIN class_templates ct ON ct.id = cs.template_id
+		WHERE cs.tenant_id = $1 AND cs.schedule_id = $2 AND cs.starts_at > $3
+		ORDER BY cs.starts_at ASC
+	`, tenantID, scheduleID, after)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var records []ClassSessionRecord
+	for rows.Next() {
+		var record ClassSessionRecord
+		if err := rows.Scan(
+			&record.ID,
+			&record.TenantID,
+			&record.TemplateID,
+			&record.LocationID,
+			&record.Title,
+			&record.StartsAt,
+			&record.EndsAt,
+			&record.Capacity,
+			&record.ScheduleID,
+		); err != nil {
+			return nil, err
+		}
+		records = append(records, record)
+	}
+	return records, rows.Err()
+}
+
+// RetimeFutureScheduleSessions shifts each future session of a rule to a new
+// local start time (keeping its calendar date) and optionally a new location.
+// Live bookings on those sessions are moved to the same window so reminders
+// and calendars stay in sync. A nil startsLocal keeps session times.
+func (r *PGRepository) RetimeFutureScheduleSessions(ctx context.Context, tenantID string, scheduleID string, startsLocal *string, locationID *string, now time.Time) error {
+	_, err := r.pool.Exec(ctx, `
+		WITH moved AS (
+			UPDATE class_sessions cs SET
+				starts_at = CASE WHEN $4::time IS NULL THEN cs.starts_at
+					ELSE ((cs.starts_at AT TIME ZONE t.timezone)::date + $4::time) AT TIME ZONE t.timezone END,
+				ends_at = CASE WHEN $4::time IS NULL THEN cs.ends_at
+					ELSE ((cs.starts_at AT TIME ZONE t.timezone)::date + $4::time) AT TIME ZONE t.timezone + make_interval(mins => tpl.duration_minutes) END,
+				location_id = CASE WHEN $5::text IS NULL THEN cs.location_id WHEN $5::text = '' THEN NULL ELSE $5::uuid END
+			FROM tenants t, class_templates tpl
+			WHERE cs.tenant_id = $1 AND cs.schedule_id = $2 AND cs.starts_at > $3
+			  AND t.id = cs.tenant_id AND tpl.id = cs.template_id
+			RETURNING cs.id, cs.starts_at, cs.ends_at
+		)
+		UPDATE bookings b SET starts_at = m.starts_at, ends_at = m.ends_at
+		FROM moved m
+		WHERE b.class_session_id = m.id AND b.status IN ('confirmed', 'waitlisted')
+	`, tenantID, scheduleID, now, startsLocal, locationID)
+	return err
+}