feat(blocks): SectionGrid/InfoCard/ContactForm + Konsolidierung (Tier 1)

Neue Komponenten: SectionGrid, InfoCard (tone/compact), ArrowLink, ContactFormBlock,
SectionGridBlock. CMS-Blöcke section_grid + contact_form (info_card-Collection).
OrganisationsBlock: presentation "grid" (SectionGrid + InfoCard-Tiles).
Kontaktformular-Submit: size md + Send-Icon.

Konsolidierung Tier 1:
- .card-surface + Card-Atom → rounded-lg, .chip → rounded-full, Input-Atome → rounded-md
- tote .btn-*-Klassen aus app.css entfernt (Atom nutzt --color-btn-*-Tokens)
- hardcoded Hex → stein-Tokens (InfoCard, ContactFormBlock)
- redundante rounded-sm auf card-surface-Nutzern entfernt

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

src/lib/components/blocks/OrganisationsBlock.svelte

@@ -10,6 +10,8 @@
   import RustyImage from "$lib/components/RustyImage.svelte";
   import Button from "$lib/ui/Button.svelte";
   import SectionHeader from "$lib/components/SectionHeader.svelte";
+  import SectionGrid from "$lib/components/SectionGrid.svelte";
+  import InfoCard from "$lib/components/InfoCard.svelte";
 
   function organisationLogoField(o: OrganisationEntry) {
     return extractCmsImageField(o.logo);
@@ -32,6 +34,8 @@
   );
   const compact = $derived(block.presentation === "compact");
   const carousel = $derived(block.presentation === "carousel");
+  // "grid" = SectionGrid + InfoCard-Tiles (Logo im Kreis, Name, Beschreibung).
+  const grid = $derived(block.presentation === "grid");
   const orgs = $derived(block.organisations ?? []);
   const ctaHtml = $derived(
     block.addOrganisationMarkdown
@@ -166,7 +170,7 @@
 {/snippet}
 
 <div class={layoutClasses} data-block="Organisations" data-block-type="organisations" data-block-slug={block._slug}>
-  {#if block.headline}
+  {#if block.headline && !grid}
     {#if compact}
       <h3 class="mb-2 text-lg font-semibold text-stein-900">{block.headline}</h3>
     {:else}
@@ -183,7 +187,29 @@
     {/if}
   {/if}
 
-  {#if carousel}
+  {#if grid}
+    <SectionGrid
+      number={block.number}
+      kicker={block.kicker}
+      title={block.headline}
+      subtitle={block.description}
+      actionLabel={actionRef?.linkName}
+      actionHref={actionRef?.url}
+      columns={3}
+    >
+      {#each orgs as org}
+        {#if typeof org === "object" && org !== null}
+          {@const o = org as OrganisationEntry}
+          {@const logoField = organisationLogoField(o)}
+          <InfoCard
+            icon={logoField?.url ?? "mdi:account-group"}
+            title={o.name ?? ""}
+            description={o.description}
+          />
+        {/if}
+      {/each}
+    </SectionGrid>
+  {:else if carousel}
     <div class="relative">
       <div
         bind:this={scroller}