feat: full dark mode with :root.dark and dark: classes

layout.css
- Change .dark → :root.dark so variable overrides match Tailwind's
  :root, :host specificity and actually take effect
- Add global dark mode styles for input/select/textarea elements

All .svelte files:
- bg-white → bg-white dark:bg-gray-100 (cards, tables, containers)
- text-white → text-white dark:text-gray-950 (button text)
- Add dark:bg-gray-950 to main page containers (dashboard, account,
  license-keys, proclamations, proclamations/[id])
- Add dark:border-gray-300 to bordered elements (cards, tables, forms)
- Add dark:bg-gray-200 to secondary backgrounds (table headers,
  address form, price badges)
- Add dark:hover:bg-gray-300 / dark:hover:bg-gray-700 to hover states
  (sidebar nav links, clear button, admin categories table)

src/routes/forgot-password/+page.svelte

@@ -30,7 +30,7 @@
 		/>
 		<button
 			type="submit"
-			class="rounded-lg bg-blue-600 px-4 py-2 font-medium text-white transition-colors hover:bg-blue-700"
+			class="rounded-lg bg-blue-600 px-4 py-2 font-medium text-white dark:text-gray-950 transition-colors hover:bg-blue-700"
 		>
 			Send Reset Link
 		</button>