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]>

web/src/lib/gardens.ts

@@ -19,6 +19,8 @@ export const gardenSchema = z.object({
   heightCm: z.number(),
   unitPref: unitPrefSchema,
   notes: z.string(),
+  gridSizeCm: z.number(),
+  snapToGrid: z.boolean(),
   version: z.number(),
   createdAt: z.string(),
   updatedAt: z.string(),
@@ -55,6 +57,8 @@ export interface GardenInput {
   heightCm: number
   unitPref: UnitPref
   notes: string
+  gridSizeCm: number
+  snapToGrid: boolean
 }
 
 export function useCreateGarden() {