Configurable grid + snap-to-grid in the layout system (#45)

Closes #44. Two independent grids (garden + per-bed), each with a size and a snap toggle; snapping defaults off. See PR #45 for details.

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

internal/service/gardens.go

@@ -13,11 +13,12 @@ import (
 // sanity range that also rejects NaN/Inf and absurd values. Name/notes are
 // length-capped so untrusted input can't balloon storage.
 const (
-	defaultGardenCM   = 1000   // 10 m
-	minGardenCM       = 1      // 1 cm
-	maxGardenCM       = 10_000 // 100 m
-	maxGardenNameLen  = 200
-	maxGardenNotesLen = 10_000
+	defaultGardenCM     = 1000   // 10 m
+	minGardenCM         = 1      // 1 cm
+	maxGardenCM         = 10_000 // 100 m
+	defaultGardenGridCM = 100    // 1 m, matching the editor's previous fixed grid
+	maxGardenNameLen    = 200
+	maxGardenNotesLen   = 10_000
 )
 
 // gardenRole ranks a user's access to a garden. Higher includes lower
@@ -48,11 +49,13 @@ func (r gardenRole) String() string {
 
 // GardenInput is the mutable field set for creating or updating a garden.
 type GardenInput struct {
-	Name     string
-	WidthCM  float64
-	HeightCM float64
-	UnitPref string
-	Notes    string
+	Name       string
+	WidthCM    float64
+	HeightCM   float64
+	UnitPref   string
+	Notes      string
+	GridSizeCM float64
+	SnapToGrid bool
 }
 
 // requireGardenRole loads a garden and enforces that the actor holds at least
@@ -163,7 +166,9 @@ func (s *Service) DeleteGarden(ctx context.Context, actorID, gardenID int64) err
 
 // gardenFromInput validates and normalizes input into a domain.Garden (without
 // identity/ownership fields). With applyDefaults, absent dimensions/unit are
-// filled in (create); without it, every field must be supplied (update).
+// filled in (create); without it, dimensions and unit must be supplied (update).
+// The grid size is the exception: 0 always means "unset" and is defaulted on both
+// paths, so an older client that omits it can't wipe the column to an invalid 0.
 func gardenFromInput(in GardenInput, applyDefaults bool) (*domain.Garden, error) {
 	name := strings.TrimSpace(in.Name)
 	if name == "" || len(name) > maxGardenNameLen {
@@ -198,12 +203,26 @@ func gardenFromInput(in GardenInput, applyDefaults bool) (*domain.Garden, error)
 		return nil, domain.ErrInvalidInput
 	}
 
+	// Grid spacing shares the garden dimension range [1 cm, 100 m]. 0 means
+	// "unset" — defaulted (not just on create: an older client that omits it must
+	// not wipe the column to an invalid 0), so a saved garden always has a usable
+	// grid even if snapping is off.
+	grid := in.GridSizeCM
+	if grid == 0 {
+		grid = defaultGardenGridCM
+	}
+	if !validDimensionCM(grid) {
+		return nil, domain.ErrInvalidInput
+	}
+
 	return &domain.Garden{
-		Name:     name,
-		WidthCM:  width,
-		HeightCM: height,
-		UnitPref: unit,
-		Notes:    notes,
+		Name:       name,
+		WidthCM:    width,
+		HeightCM:   height,
+		UnitPref:   unit,
+		Notes:      notes,
+		GridSizeCM: grid,
+		SnapToGrid: in.SnapToGrid,
 	}, nil
 }