Address Gadfly review on #12: helper naming + FK-backstop test

- Rename test helper intPtr → ptrInt to match the package's ptrBool sibling
  (2/5 reviewers flagged the naming inconsistency).
- Add a store-level test that drives DeletePlant into the ON DELETE RESTRICT
  foreign key so the isForeignKeyViolation string-match (→ ErrPlantInUse) is
  pinned; a driver-message change now fails here, not as a prod 500.

Skipped (advisory, non-blocking): the parseNullableInt/parseNullableString
generic-helper refactor (cosmetic, touches working code) and the documented
LIMIT 5000 backstop.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

internal/store/store_test.go

@@ -2,9 +2,12 @@ package store
 
 import (
 	"context"
+	"errors"
 	"path/filepath"
 	"strings"
 	"testing"
+
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
 )
 
 // openTestDB opens a fresh file-backed DB in a temp dir and migrates it.
@@ -88,6 +91,44 @@ func TestForeignKeysEnforced(t *testing.T) {
 	}
 }
 
+func TestDeletePlantForeignKeyBackstop(t *testing.T) {
+	db := openTestDB(t)
+	ctx := context.Background()
+
+	// Seed a user → garden → object → custom plant, then a planting referencing
+	// the plant. DeletePlant must surface the ON DELETE RESTRICT FK as
+	// ErrPlantInUse (not a raw 500-worthy error) — this pins isForeignKeyViolation's
+	// string-match so a driver-message change is caught here rather than in prod.
+	// The service normally blocks this via a count pre-check; here we hit the
+	// store backstop directly (the lost-race path).
+	insert := func(q string, args ...any) int64 {
+		res, err := db.SQL().ExecContext(ctx, q, args...)
+		if err != nil {
+			t.Fatalf("seed exec %q: %v", q, err)
+		}
+		id, err := res.LastInsertId()
+		if err != nil {
+			t.Fatalf("last insert id: %v", err)
+		}
+		return id
+	}
+	uid := insert(`INSERT INTO users (email, display_name) VALUES ('[email protected]', 'A')`)
+	gid := insert(`INSERT INTO gardens (owner_id, name, width_cm, height_cm) VALUES (?, 'G', 100, 100)`, uid)
+	oid := insert(`INSERT INTO garden_objects (garden_id, kind, x_cm, y_cm, width_cm, height_cm) VALUES (?, 'bed', 0, 0, 10, 10)`, gid)
+	pid := insert(`INSERT INTO plants (owner_id, name, category, spacing_cm, color, icon) VALUES (?, 'Basil', 'herb', 25, '#4a7c3f', '🌿')`, uid)
+	insert(`INSERT INTO plantings (object_id, plant_id, x_cm, y_cm, radius_cm) VALUES (?, ?, 0, 0, 10)`, oid, pid)
+
+	if err := db.DeletePlant(ctx, pid); !errors.Is(err, domain.ErrPlantInUse) {
+		t.Fatalf("DeletePlant on referenced plant = %v, want ErrPlantInUse", err)
+	}
+
+	// Clearing the reference lets the delete succeed.
+	insert(`DELETE FROM plantings WHERE plant_id = ?`, pid)
+	if err := db.DeletePlant(ctx, pid); err != nil {
+		t.Errorf("DeletePlant after clearing reference: %v", err)
+	}
+}
+
 func TestCheckConstraintRejectsBadEnum(t *testing.T) {
 	db := openTestDB(t)