feat(design-system): Storybook + Button-Atom-Vereinheitlichung + SectionHeader

Storybook (SvelteKit-Framework, Tailwind v4, MSW, Translation-Decorator):
Stories für Atoms/Molecules/Organisms + alle CMS-Blocks.

Button-Atom: 5 .btn-*-Varianten (primary/secondary/tertiary/outline/warning),
class-Merge-Prop, href→<a>, Loading-Spinner neben Label, rounded-md/font-medium.
Alle rohen .btn-*- und Hand-Style-Buttons app-weit aufs Atom migriert.

SectionHeader-Molecule (kicker/number/title/subtitle/action) + Integration in
7 CMS-Blocks (post_overview, organisations, organisations_map, searchable_text,
image_gallery, youtube_video_gallery, files) via neuem section_header-Schema.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/components/blocks/OrganisationsMapBlock.svelte

@@ -2,14 +2,19 @@
   import "leaflet/dist/leaflet.css";
   import { onMount, onDestroy } from "svelte";
   import { getBlockLayoutClasses } from "$lib/block-layout";
+  import SectionHeader from "$lib/components/SectionHeader.svelte";
   import type { OrganisationsMapBlockData, OrganisationEntry, ContactEntry } from "$lib/block-types";
   import Icon from "@iconify/svelte";
   import "$lib/iconify-offline";
   import { marked } from "$lib/markdown-safe";
+  import Button from "$lib/ui/Button.svelte";
 
   let { block }: { block: OrganisationsMapBlockData } = $props();
 
   const layoutClasses = $derived(getBlockLayoutClasses(block.layout));
+  const actionRef = $derived(
+    block.action && typeof block.action === "object" ? block.action : null,
+  );
 
   const orgs = $derived(
     (block.organisations ?? []).filter(
@@ -127,7 +132,15 @@
 
 <div class="not-prose {layoutClasses}" data-block-type="organisations_map">
   {#if block.headline}
-    <h2 class="mb-3 text-xl font-bold text-stein-900">{block.headline}</h2>
+    <div class="mb-3">
+      <SectionHeader
+        number={block.number}
+        kicker={block.kicker}
+        title={block.headline}
+        actionLabel={actionRef?.linkName}
+        actionHref={actionRef?.url}
+      />
+    </div>
   {/if}
 
   <div
@@ -222,15 +235,17 @@
           {/if}
 
           {#if getLink(selectedOrg)}
-            <a
-              href={getLink(selectedOrg)}
+            <Button
+              href={getLink(selectedOrg) ?? undefined}
+              variant="outline"
+              size="sm"
               target="_blank"
               rel="noopener noreferrer"
-              class="btn-outline btn-sm w-full justify-center no-underline!"
+              class="w-full"
             >
               <Icon icon="lucide:external-link" class="size-3.5" />
               {getLinkLabel(selectedOrg)}
-            </a>
+            </Button>
           {/if}
         </div>
       </div>