Add webhook-event retention job, schema, and testdb pre-flight hint

square_webhook_events is now CREATE TABLE IF NOT EXISTS, registered as the 24th maintenance job (sweep-square-webhook-events, daily 2:30am) pruning rows older than 90 days, and testdb gives a clear docker compose hint when the admin DB connection fails.

backend/internal/jobs/cleanup.go

@@ -1,14 +1,21 @@
 package jobs
 
 import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
 	"time"
 
 	"crussell/auth"
+	"crussell/db"
 	authHandlers "crussell/handlers/auth"
 	"crussell/handlers/payments"
 	"crussell/handlers/scheduling"
 	"crussell/handlers/user"
 	"crussell/mw"
+
+	"github.com/jackc/pgx/v5"
 )
 
 // RegisterAll registers every background maintenance job on the scheduler.
@@ -214,4 +221,41 @@ func RegisterAll(s *Scheduler) {
 		Concurrency: 1,
 		Handler:     scheduling.CleanupExpiredRefreshTokens,
 	})
+
+	// Staggered from cleanup-verification-codes / cleanup-refresh-tokens
+	// (both at 0 2 * * *) to avoid DB contention.
+	s.Register(Job{
+		Name:        "sweep-square-webhook-events",
+		Schedule:    "30 2 * * *", // Daily at 2:30am
+		Timeout:     30 * time.Second,
+		Concurrency: 1,
+		Handler:     SweepSquareWebhookEvents,
+	})
+}
+
+// SweepSquareWebhookEvents deletes square_webhook_events rows older than 90
+// days. Every accepted webhook event_id is stored permanently for restart-safe
+// dedup (payment.updated fires on every payment update), so without retention
+// the table would grow without bound. 90 days comfortably exceeds Square's
+// webhook replay window while keeping the table bounded.
+func SweepSquareWebhookEvents(ctx context.Context) (int, error) {
+	tx, err := db.Conn.Begin(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("failed to begin transaction: %w", err)
+	}
+	defer func() {
+		if err := tx.Rollback(ctx); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
+			slog.Error("failed to rollback transaction", "err", err)
+		}
+	}()
+
+	tag, err := tx.Exec(ctx, `
+		DELETE FROM square_webhook_events
+		WHERE received_at < NOW() - INTERVAL '90 days'
+	`)
+	if err != nil {
+		return 0, fmt.Errorf("failed to sweep square webhook events: %w", err)
+	}
+
+	return int(tag.RowsAffected()), tx.Commit(ctx)
 }