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/routes/+layout.svelte

@@ -271,18 +271,18 @@
 <TranslationProvider translations={data.translations}>
   <a
     href="#main-content"
-    class="sr-only focus:not-sr-only focus:fixed focus:top-2 focus:left-2 focus:z-[100] focus:bg-white focus:px-3 focus:py-2 focus:shadow focus:outline focus:outline-2 focus:outline-wald-600 focus:rounded-sm"
+    class="sr-only focus:not-sr-only focus:fixed focus:top-2 focus:left-2 focus:z-[100] focus:bg-white focus:px-3 focus:py-2 focus:shadow focus:outline focus:outline-2 focus:outline-wald-600 focus:rounded-xs"
   >Zum Inhalt springen</a>
-  <div class="flex min-h-screen flex-col text-zinc-900">
+  <div class="flex min-h-screen flex-col text-stein-900">
     {#if pageData?.preview || pageData?.previewDraft}
       <div
-        class="sticky top-0 z-[90] w-full bg-amber-500 text-black shadow-sm"
+        class="sticky top-0 z-[90] w-full bg-erde-500 text-black shadow-sm"
         role="status"
         aria-live="polite"
       >
         <div class="container-custom flex items-center justify-between gap-3 py-1.5 text-sm">
           <span class="font-semibold">
-            {pageData?.previewDraft ? 'Live-Preview — ungespeicherter Draft' : 'Preview-Modus — Draft sichtbar (nicht indexiert)'}
+            {pageData?.previewDraft ? 'Live-Preview · ungespeicherter Draft' : 'Preview-Modus · Draft sichtbar (nicht indexiert)'}
           </span>
           <a
             href={$page.url.pathname}