refactor: tailwind tier 1 — border-subtle/text-secondary/focus-ring utilities + Input config extraction

src/shared/ui/Button/Button.svelte

@@ -111,7 +111,7 @@ const variantStyles: Record<ButtonVariant, string> = {
     ),
     ghost: cn(
         'bg-transparent',
-        'text-neutral-500 dark:text-neutral-400',
+        'text-secondary',
         'border border-transparent',
         'hover:bg-transparent dark:hover:bg-transparent',
         'hover:text-brand dark:hover:text-brand',
@@ -121,7 +121,7 @@ const variantStyles: Record<ButtonVariant, string> = {
     ),
     icon: cn(
         'bg-surface dark:bg-dark-bg',
-        'text-neutral-500 dark:text-neutral-400',
+        'text-secondary',
         'border border-transparent',
         'hover:bg-paper dark:hover:bg-paper',
         'hover:text-brand',
@@ -172,7 +172,7 @@ const activeStyles: Partial<Record<ButtonVariant, string>> = {
         'bg-paper dark:bg-dark-card border-black/10 dark:border-white/10 shadow-sm text-neutral-900 dark:text-neutral-100',
     ghost: 'bg-transparent dark:bg-transparent text-brand dark:text-brand',
     outline: 'bg-surface dark:bg-paper border-brand',
-    icon: 'bg-paper dark:bg-paper text-brand border-black/5 dark:border-white/10',
+    icon: 'bg-paper dark:bg-paper text-brand border-subtle',
 };
 
 const classes = $derived(cn(
@@ -184,7 +184,7 @@ const classes = $derived(cn(
     'select-none',
     'outline-none',
     'cursor-pointer',
-    'focus-visible:ring-2 focus-visible:ring-brand focus-visible:ring-offset-2',
+    'focus-ring',
     'focus-visible:ring-offset-surface dark:focus-visible:ring-offset-dark-bg',
     'disabled:cursor-not-allowed disabled:pointer-events-none',
     // Variant