Address Gadfly review on the garden copy

* api: detect an absent copy body by io.EOF from the decoder rather than
  Content-Length. A chunked request reports -1, not 0, so the length test
  read an empty chunked body as malformed and 400'd instead of taking the
  default-name path. Covered by a new unknown-length test.

* store: hoist the garden_objects/plantings INSERTs into shared
  objectInsert/plantingInsert statements with matching *InsertArgs
  helpers. CopyGarden had its own copies of both column lists, so a
  column added to the table could be wired into Create* and silently
  dropped from a copy.

* store: move the queryer interface to sqlite.go, next to the other
  shared query plumbing, instead of users.go.

* web: derive a copy's prefilled name via defaultCopyName, mirroring the
  server's copyName including its 200-BYTE cap. The inline
  `${name} (copy)` both duplicated the suffix and, for a garden whose
  name was already at the cap, prefilled an over-long name that the
  server rejected with a 400. Unit-tested, including multi-byte
  truncation on a code-point boundary.

* test: drop a throwaway `_ = kept`.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

internal/store/plantings.go

@@ -104,16 +104,25 @@ func (d *DB) GetPlanting(ctx context.Context, id int64) (*domain.Planting, error
 	return p, nil
 }
 
+// plantingInsert inserts one plantings row and returns it. Shared by
+// CreatePlanting, the CreatePlantings batch and CopyGarden's in-transaction copy
+// — with plantingInsertArgs supplying its parameters — so all three stay in step
+// with the table. removed_at is never set here: a new plop is active, and "clear
+// bed" sets removed_at later via UpdatePlanting.
+const plantingInsert = `INSERT INTO plantings (object_id, plant_id, x_cm, y_cm, radius_cm, count, label, planted_at)
+	 VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+	 RETURNING ` + plantingColumns
+
+// plantingInsertArgs builds plantingInsert's parameters, parenting p to objectID
+// (p's own object normally, and the copied object when copying a garden).
+func plantingInsertArgs(objectID int64, p *domain.Planting) []any {
+	return []any{objectID, p.PlantID, p.XCM, p.YCM, p.RadiusCM, p.Count, p.Label, p.PlantedAt}
+}
+
 // CreatePlanting inserts a plop (fields already validated by the service) and
-// returns the stored row. removed_at is always NULL on create — a new plop is
-// active; "clear bed" sets removed_at later via UpdatePlanting.
+// returns the stored row.
 func (d *DB) CreatePlanting(ctx context.Context, p *domain.Planting) (*domain.Planting, error) {
-	created, err := scanPlanting(d.sql.QueryRowContext(ctx,
-		`INSERT INTO plantings (object_id, plant_id, x_cm, y_cm, radius_cm, count, label, planted_at)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)
-		 RETURNING `+plantingColumns,
-		p.ObjectID, p.PlantID, p.XCM, p.YCM, p.RadiusCM, p.Count, p.Label, p.PlantedAt,
-	))
+	created, err := scanPlanting(d.sql.QueryRowContext(ctx, plantingInsert, plantingInsertArgs(p.ObjectID, p)...))
 	if err != nil {
 		return nil, fmt.Errorf("store: insert planting: %w", err)
 	}
@@ -132,13 +141,9 @@ func (d *DB) CreatePlantings(ctx context.Context, plantings []*domain.Planting)
 	}
 	defer tx.Rollback() //nolint:errcheck // no-op after a successful commit
 
-	const stmt = `INSERT INTO plantings (object_id, plant_id, x_cm, y_cm, radius_cm, count, label, planted_at)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)
-		 RETURNING ` + plantingColumns
 	out := make([]domain.Planting, 0, len(plantings))
 	for _, p := range plantings {
-		created, err := scanPlanting(tx.QueryRowContext(ctx, stmt,
-			p.ObjectID, p.PlantID, p.XCM, p.YCM, p.RadiusCM, p.Count, p.Label, p.PlantedAt))
+		created, err := scanPlanting(tx.QueryRowContext(ctx, plantingInsert, plantingInsertArgs(p.ObjectID, p)...))
 		if err != nil {
 			return nil, fmt.Errorf("store: insert planting (batch): %w", err)
 		}