feat(ui): deadline banner with gradient blob bg, swap Lora→Aleo

- DeadlineBannerBlock: redesign nach Tailwind-UI-Vorlage (gray-50, blurry blobs, dismiss button)
- new .gradient-blob-bg utility (radial-gradient blobs via ::before/::after)
- apply blob bg to Header
- @theme: register --font-sans (Inter) + --font-serif (Aleo)
- replace @fontsource-variable/lora with /aleo for blockquote font
- Header: simplify active nav-link styling
- QuoteBlock: formatting + drop borderClass

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -37,7 +37,7 @@
     "vitest": "^2.1.9"
   },
   "dependencies": {
-    "@fontsource-variable/lora": "^5.2.8",
+    "@fontsource-variable/aleo": "^5.2.7",
     "@fontsource-variable/rubik": "^5.2.8",
     "@fontsource/inter": "^5.2.8",
     "@iconify/svelte": "^5.2.1",