fix(styles): resolve design system audit violations

- Replace off-grid spacing (3px, 5px) with space tokens (--space-0h, --space-1)
- Replace below-minimum font-size 9px with var(--text-xs) in calendar, dashboard, notes
- Replace hardcoded 2.5rem with var(--text-4xl) in weather widget
- Replace hardcoded box-shadow with var(--shadow-sm) in toggle thumb
- Replace 0.85em and #666 with type/color tokens in print styles

public/styles/tasks.css

@@ -56,7 +56,7 @@
   display: flex;
   background-color: var(--color-surface-2);
   border-radius: var(--radius-sm);
-  padding: 3px;
+  padding: var(--space-0h);
   gap: 2px;
 }
 
@@ -467,7 +467,7 @@
   justify-content: center;
   min-width: 18px;
   height: 18px;
-  padding: 0 5px;
+  padding: 0 var(--space-1);
   border-radius: var(--radius-full);
   background-color: var(--color-danger);
   color: #fff;