css: replace hardcoded values with design tokens

Replace 30 border-radius: 1000px → var(--radius-pill), 6 border-radius:
20px → var(--radius-card), 21 transition: 100ms → var(--transition-fast),
and 32 transition: 200ms → var(--transition-normal) across the codebase.

src/lib/components/LinksGrid.svelte

@@ -20,7 +20,7 @@
 :global(a){
 	text-decoration: unset;
 	color: var(--nord0);
-	transition: 200ms;
+	transition: var(--transition-normal);
 }
 :global(.links_grid a:hover){
 	box-shadow: 1em 1em 2em 1em rgba(0,0,0, 0.3);
@@ -43,7 +43,7 @@
 	justify-content: center;
 	text-decoration: unset;
 	color: var(--nord0);
-	transition: 200ms;
+	transition: var(--transition-normal);
 	width: 100%;
 	padding: 1rem;
 	position: relative;