Plantings backend: plop CRUD, derived counts, removed_at (#14)

Co-authored-by: Steve Dudenhoeffer <[email protected]>

internal/service/objects.go

@@ -69,8 +69,8 @@ type ObjectPatch struct {
 }
 
 // FullGarden is the one-shot editor payload: the garden plus everything drawn in
-// it. Plantings/Plants stay empty until #14 populates plantings; the shape is
-// fixed now so the frontend types against it once.
+// it — objects, active plantings (each with its DerivedCount filled in), and the
+// plants those plantings reference.
 type FullGarden struct {
 	Garden    *domain.Garden        `json:"garden"`
 	Objects   []domain.GardenObject `json:"objects"`
@@ -176,6 +176,15 @@ func (s *Service) GardenFull(ctx context.Context, actorID, gardenID int64) (*Ful
 	if err != nil {
 		return nil, err
 	}
+	// Fill each plop's DerivedCount from its plant's spacing (referenced plants
+	// are already loaded, so this is a map lookup rather than N queries).
+	spacing := make(map[int64]float64, len(plants))
+	for _, pl := range plants {
+		spacing[pl.ID] = pl.SpacingCM
+	}
+	for i := range plantings {
+		plantings[i].DerivedCount = derivedCount(plantings[i].RadiusCM, spacing[plantings[i].PlantID])
+	}
 	return &FullGarden{Garden: g, Objects: objects, Plantings: plantings, Plants: plants}, nil
 }