feat: overhaul TODO.md and enhance Kanban components

- Updated TODO.md to reflect the new project structure and phases, marking several tasks as completed.
- Enhanced Kanban components with a tech-inspired design, including new styles for columns and task cards.
- Removed the obsolete reminders service and task processor, streamlining the codebase for better maintainability.
- Introduced a modern API for task management, including CRUD operations and improved error handling.
- Updated global styles for a cohesive dark theme and added custom scrollbar styles.

components/kanban/Board.tsx

@@ -56,16 +56,19 @@ export function KanbanBoard({ tasks }: KanbanBoardProps) {
   ];
 
   return (
-    <div className="w-full flex gap-4 overflow-x-auto pb-6">
-      {columns.map((column) => (
-        <KanbanColumn
-          key={column.id}
-          id={column.id}
-          title={column.title}
-          color={column.color}
-          tasks={column.tasks}
-        />
-      ))}
+    <div className="h-full flex flex-col bg-slate-950">
+      {/* Board tech dark */}
+      <div className="flex-1 flex gap-6 overflow-x-auto p-6">
+        {columns.map((column) => (
+          <KanbanColumn
+            key={column.id}
+            id={column.id}
+            title={column.title}
+            color={column.color}
+            tasks={column.tasks}
+          />
+        ))}
+      </div>
     </div>
   );
 }