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

src/stores/board-store.ts

@@ -26,6 +26,7 @@ interface BoardActions {
   deleteColumn: (columnId: string) => void;
   moveColumn: (fromIndex: number, toIndex: number) => void;
   setColumnWidth: (columnId: string, width: ColumnWidth) => void;
+  setColumnColor: (columnId: string, color: string | null) => void;
 
   addCard: (columnId: string, title: string) => string;
   updateCard: (cardId: string, updates: Partial<Card>) => void;
@@ -130,6 +131,7 @@ export const useBoardStore = create<BoardState & BoardActions>()(
               title,
               cardIds: [],
               width: "standard" as ColumnWidth,
+              color: null,
             },
           ],
         }));
@@ -179,6 +181,16 @@ export const useBoardStore = create<BoardState & BoardActions>()(
         }));
       },
 
+      setColumnColor: (columnId, color) => {
+        mutate(get, set, (b) => ({
+          ...b,
+          updatedAt: now(),
+          columns: b.columns.map((c) =>
+            c.id === columnId ? { ...c, color } : c
+          ),
+        }));
+      },
+
       // -- Card actions --
 
       addCard: (columnId, title) => {
@@ -191,6 +203,7 @@ export const useBoardStore = create<BoardState & BoardActions>()(
           checklist: [],
           dueDate: null,
           attachments: [],
+          coverColor: null,
           createdAt: now(),
           updatedAt: now(),
         };