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/PostActions.svelte

@@ -154,19 +154,19 @@
       onclick={onCommentClick}
       aria-label={t(T.comments_jump_to)}
       title={t(T.comments_jump_to)}
-      class="no-underline! inline-flex items-center gap-1 rounded-full border border-zinc-200 bg-white px-2.5 py-1 text-xs font-medium text-zinc-700! hover:bg-zinc-50 hover:border-zinc-300 transition-colors"
+      class="no-underline! inline-flex items-center gap-1 rounded-full border border-stein-200 bg-white px-2.5 py-1 text-xs font-medium text-stein-700! hover:bg-stein-50 hover:border-stein-300 transition-colors"
     >
       <Icon icon="mdi:comment-outline" class="size-3.5" />
       <span class="tabular-nums">{commentCount ?? "…"}</span>
     </a>
   {/if}
 
-  <div class="inline-flex items-center rounded-full border border-zinc-200 bg-white overflow-hidden divide-x divide-zinc-200 print:hidden">
+  <div class="inline-flex items-center rounded-full border border-stein-200 bg-white overflow-hidden divide-x divide-stein-200 print:hidden">
     {#if canShare}
       <button
         type="button"
         onclick={share}
-        class="inline-flex items-center px-2.5 py-1 text-zinc-600 hover:bg-zinc-50 hover:text-zinc-900 transition-colors"
+        class="inline-flex items-center px-2.5 py-1 text-stein-600 hover:bg-stein-50 hover:text-stein-900 transition-colors"
         aria-label={t(T.post_action_share)}
         title={t(T.post_action_share)}
       >
@@ -179,7 +179,7 @@
     <button
       type="button"
       onclick={copyLink}
-      class="inline-flex items-center px-2.5 py-1 text-zinc-600 hover:bg-zinc-50 hover:text-zinc-900 transition-colors"
+      class="inline-flex items-center px-2.5 py-1 text-stein-600 hover:bg-stein-50 hover:text-stein-900 transition-colors"
       aria-label={copied ? t(T.post_action_copied) : t(T.post_action_copy)}
       title={copied ? t(T.post_action_copied) : t(T.post_action_copy)}
     >
@@ -188,7 +188,7 @@
     <button
       type="button"
       onclick={print}
-      class="inline-flex items-center px-2.5 py-1 text-zinc-600 hover:bg-zinc-50 hover:text-zinc-900 transition-colors"
+      class="inline-flex items-center px-2.5 py-1 text-stein-600 hover:bg-stein-50 hover:text-stein-900 transition-colors"
       aria-label={t(T.post_action_print)}
       title={t(T.post_action_print)}
     >
@@ -198,7 +198,7 @@
 
   {#if readingTimeMinutes != null && readingTimeMinutes > 0}
     <span
-      class="inline-flex items-center gap-1 rounded-full border border-zinc-200 bg-white px-2.5 py-1 text-xs text-zinc-500"
+      class="inline-flex items-center gap-1 rounded-full border border-stein-200 bg-white px-2.5 py-1 text-xs text-stein-500"
       title={t(T.post_action_reading_time, { minutes: readingTimeMinutes })}
     >
       <Icon icon="mdi:clock-outline" class="size-3.5" />