style(design): consistency sweep + UX upgrades

- Palette: gray/zinc/slate/neutral → stein, red → fire, amber → erde,
  sky → himmel, green → wald
- Footer: replaced raw rgb with stein tokens
- Radius: unified to rounded-xs across cards, buttons, inputs, pagination
- Buttons: .btn-primary/.btn-secondary now font-medium; added secondary
- Card hover: -translate-y-0.5 + shadow + wald-300 border
- Header active link: wald border-bottom + wald-700 text
- Mobile nav: bigger touch targets + wald active accent
- Pagination: prev/next text labels + wald-500 active state with
  separated shape/color classes to avoid Tailwind conflicts
- Lead paragraph: scoped .markdown > p:first-child for top-level
  MarkdownBlock only via [data-block-type="markdown"]
- Section dividers: subtle wald-200 gradient between content rows
- Global focus-visible ring (wald-500)
- Inline hex → palette tokens (Badge amber, Tag custom-color contrast)
- Font weights snapped to design system (300/400/500/600/700)
- transition-all → transition-colors where only color changes
- Removed em-dashes from user-visible templates

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

src/lib/components/blocks/ImageGalleryBlock.svelte

@@ -174,7 +174,7 @@
         <li class="m-0 p-0">
           <button
             type="button"
-            class="group relative block w-full aspect-square overflow-hidden rounded-sm bg-wald-100 p-2 cursor-zoom-in focus:outline-none focus:ring-2 focus:ring-wald-500"
+            class="group relative block w-full aspect-square overflow-hidden rounded-xs bg-wald-100 p-2 cursor-zoom-in focus:outline-none focus:ring-2 focus:ring-wald-500"
             onclick={() => openModal(i)}
             aria-label={label || t(T.image_gallery_open_aria)}
           >
@@ -220,7 +220,7 @@
           <img
             src={cur.url}
             alt={curLabel}
-            class="max-h-[80vh] max-w-full rounded-sm bg-stein-900 object-contain shadow-2xl"
+            class="max-h-[80vh] max-w-full rounded-xs bg-stein-900 object-contain shadow-2xl"
             loading="eager"
           />
           <div class="flex w-full items-center justify-between gap-3 text-white">
@@ -281,7 +281,7 @@
         fit="cover"
         quality={80}
         alt={withUrl[0].img.description ?? ""}
-        class="w-full rounded-sm object-cover aspect-video"
+        class="w-full rounded-xs object-cover aspect-video"
         loading="eager"
       />
       {#if withUrl[0].img.description}
@@ -291,7 +291,7 @@
   {:else}
     <div class="group relative">
       <div
-        class="relative overflow-hidden rounded-sm bg-stein-100 aspect-video touch-pan-y cursor-grab active:cursor-grabbing"
+        class="relative overflow-hidden rounded-xs bg-stein-100 aspect-video touch-pan-y cursor-grab active:cursor-grabbing"
         role="region"
         aria-label={t(T.image_gallery_swipe_aria)}
         onpointerdown={onPointerDown}