Consistent padding (vibe-kanban) (#102)

* Fixed the uneven padding by increasing the bottom padding from `pb-3` to `pb-6` on the CardHeader, which will make the bottom padding consistent with the default top padding.

* No, we don't need custom padding. The CardHeader component from shadcn/ui already has consistent default padding that should work perfectly fine without any custom classes.

frontend/src/components/projects/project-list.tsx

@@ -167,7 +167,7 @@ export function ProjectList() {
               className="hover:shadow-md transition-shadow cursor-pointer"
               onClick={() => navigate(`/projects/${project.id}/tasks`)}
             >
-              <CardHeader className="pb-3">
+              <CardHeader>
                 <div className="flex items-start justify-between">
                   <CardTitle className="text-lg">{project.name}</CardTitle>
                   <div className="flex items-center gap-2">