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/OrganisationsBlock.stories.ts

@@ -0,0 +1,53 @@
+import type { Meta, StoryObj } from '@storybook/sveltekit';
+import OrganisationsBlock from './OrganisationsBlock.svelte';
+
+const CMS_ASSET =
+  'https://cms.pm86.de/api/assets/pages/img_2814-ar4x2.webp?_environment=windwiderstand';
+
+const meta = {
+  title: 'CMS-Blocks/Organisations',
+  component: OrganisationsBlock,
+  tags: ['autodocs'],
+  argTypes: { block: { control: 'object' } },
+} satisfies Meta<typeof OrganisationsBlock>;
+
+export default meta;
+type Story = StoryObj<typeof meta>;
+
+const organisations = [
+  {
+    name: 'BI Steigerwald',
+    logo: { src: CMS_ASSET, description: 'Logo' },
+    description: 'Bürgerinitiative für den Erhalt des Waldes.',
+    link: { url: 'https://windwiderstand.de', linkName: 'Website', newTab: true },
+    location: { text: 'Schleusingen', lat: 50.5, lng: 10.75 },
+  },
+  {
+    name: 'Waldfreunde e.V.',
+    logo: { src: CMS_ASSET, description: 'Logo' },
+    description: 'Naturschutzverein der Region.',
+    link: { url: 'https://nabu.de', linkName: 'Website', newTab: true },
+    location: { text: 'Ebrach' },
+  },
+];
+
+export const Grid: Story = {
+  args: {
+    block: {
+      number: '03',
+      kicker: 'Vor Ort',
+      headline: 'Beteiligte Organisationen',
+      action: { url: '/adressbuch', linkName: 'Zum Adressbuch' },
+      presentation: 'default',
+      organisations,
+    },
+  },
+};
+
+export const Kompakt: Story = {
+  args: { block: { headline: 'Organisationen', presentation: 'compact', organisations } },
+};
+
+export const Carousel: Story = {
+  args: { block: { headline: 'Organisationen', presentation: 'carousel', organisations } },
+};