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>

src/lib/components/Header.svelte

@@ -100,7 +100,7 @@
 
 <header
     id="horizontal-navigation"
-    class="sticky top-0 z-20 border-b border-white/30 shadow-2xl backdrop-blur-md bg-wald-50"
+    class="gradient-blob-bg sticky top-0 z-20 border-b border-white/30 shadow-2xl backdrop-blur-md bg-wald-50"
 >
     <div class="flex items-center justify-between container-custom py-2">
         <a
@@ -129,9 +129,7 @@
                 {@const active = isActiveLink(link.href, $page.url.pathname)}
                 <a
                     href={link.href}
-                    class="text-[.7rem] py-1 transition-colors hover:text-wald-700 {active
-                        ? 'font-bold text-wald-700 border-b-2 border-wald-600'
-                        : 'border-b-2 border-transparent'}"
+                    class="text-[.7rem] py-1 {active ? 'font-bold  ' : ''}"
                     aria-current={active ? "page" : undefined}
                 >
                     {link.label}
@@ -242,13 +240,16 @@
                 aria-label={t(T.header_nav_aria)}
             >
                 {#each links as link}
-                    {@const active = isActiveLink(link.href, $page.url.pathname)}
+                    {@const active = isActiveLink(
+                        link.href,
+                        $page.url.pathname,
+                    )}
                     <a
                         href={link.href}
                         class="block py-4 px-3 rounded-xs transition-colors text-base {active
                             ? 'font-bold text-wald-300 bg-wald-700/20 border-l-4 border-wald-400'
                             : 'text-stein-100 hover:text-stein-0 hover:bg-stein-0/10 border-l-4 border-transparent'}"
-                        aria-current={active ? 'page' : undefined}
+                        aria-current={active ? "page" : undefined}
                         onclick={closeMenu}
                     >
                         {link.label}