feat: add clsx and tailwind-merge dependencies, enhance Kanban components

- Added `clsx` and `tailwind-merge` to `package.json` and `package-lock.json` for improved class management and utility merging.
- Updated `Column` and `TaskCard` components to utilize new UI components (`Card`, `Badge`) for a more cohesive design.
- Refactored styles in `Header` and Kanban components to align with the new design system.
- Marked several tasks as completed in `TODO.md` reflecting progress on UI enhancements.

package.json

@@ -10,12 +10,14 @@
   },
   "dependencies": {
     "@prisma/client": "^6.16.1",
+    "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
     "next": "15.5.3",
     "prisma": "^6.16.1",
     "react": "19.1.0",
     "react-dom": "19.1.0",
-    "sqlite3": "^5.1.7"
+    "sqlite3": "^5.1.7",
+    "tailwind-merge": "^3.3.1"
   },
   "devDependencies": {
     "@eslint/eslintrc": "^3",