feat: add column color, card coverColor, and board background to data model

src/types/board.ts

@@ -15,6 +15,7 @@ export interface Column {
   title: string;
   cardIds: string[];
   width: ColumnWidth;
+  color: string | null;
 }
 
 export type ColumnWidth = "narrow" | "standard" | "wide";
@@ -27,6 +28,7 @@ export interface Card {
   checklist: ChecklistItem[];
   dueDate: string | null;
   attachments: Attachment[];
+  coverColor: string | null;
   createdAt: string;
   updatedAt: string;
 }
@@ -52,6 +54,7 @@ export interface Attachment {
 
 export interface BoardSettings {
   attachmentMode: "link" | "copy";
+  background: "none" | "dots" | "grid" | "gradient";
 }
 
 export interface BoardMeta {