Adds POST /gardens/:id/copy: duplicates a garden the actor owns, along
with its objects and their currently-planted plops, into a new garden
owned by the actor. A blank name derives "<source> (copy)".

Deliberately not carried over:
  * public_token — the share link is a capability granted to the
    original; a copy must not silently inherit a live public URL
  * garden_shares — a copy is private to whoever made it
  * removed plantings — the copy is a fresh layout, not a history

Owner-only for now: a copy's plops keep pointing at the SOURCE's
plant_ids, so letting a viewer copy someone else's garden would hand
them plants outside their catalog and pin the original owner's plants
against deletion (plantings.plant_id is ON DELETE RESTRICT). Copying a
shared garden needs a plant-cloning policy first.

The whole copy runs in one transaction, so a failure part-way leaves no
half-populated garden. The object/planting list scans are factored into
queryObjects/queryPlantings so the same code serves a plain read and a
read inside that transaction.

UI: a Copy action on the owner's garden card opens a modal prefilled
with the derived name, then lands in the new garden.

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

@@ -106,0 +117,4 @@
+	// The body is optional — POST with no body means "copy under the default
+	// name" — so only decode when one was actually sent.
+	var req gardenCopyRequest
+	if c.Request.ContentLength != 0 {

@@ -252,0 +345,4 @@
+	bed := seedBed(t, s, owner, src.ID)
+	plant := seedOwnPlant(t, s, owner, 20)
+
+	kept, err := s.CreatePlanting(ctx, owner, bed.ID, PlantingInput{PlantID: plant.ID, RadiusCM: 10})

@@ -252,0 +361,4 @@
+	if err != nil {
+		t.Fatalf("CreatePlanting(replanted): %v", err)
+	}
+	_ = kept

@@ -166,0 +213,4 @@
+	// re-parented onto the right new object.
+	objectIDs := make(map[int64]int64, len(srcObjects))
+	for _, o := range srcObjects {
+		copied, err := scanObject(tx.QueryRowContext(ctx,

@@ -19,6 +19,12 @@ type scanner interface {
 	Scan(dest ...any) error
 }
 
+// queryer is the read surface shared by *sql.DB and *sql.Tx, so a list helper can

@@ -0,0 +17,4 @@
+export function CopyGardenModal({ garden, onClose }: { garden: Garden; onClose: () => void }) {
+  const copy = useCopyGarden()
+  const navigate = useNavigate()
+  const [name, setName] = useState(`${garden.name} (copy)`)