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/SectionHeader.svelte

@@ -9,6 +9,7 @@
    *     actionLabel="Zum Adressbuch" actionHref="/adressbuch" />
    */
   import type { Snippet } from 'svelte';
+  import ArrowLink from '$lib/components/ArrowLink.svelte';
 
   let {
     number = undefined,
@@ -69,13 +70,7 @@
       {#if children}
         {@render children()}
       {:else}
-        <a
-          href={actionHref}
-          class="inline-flex items-center gap-1.5 text-[15px] font-semibold text-himmel-500 no-underline hover:text-himmel-600"
-        >
-          {actionLabel}
-          <svg class="size-4" viewBox="0 0 24 24" fill="none" aria-hidden="true"><path d="M5 12h14M13 6l6 6-6 6" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"/></svg>
-        </a>
+        <ArrowLink href={actionHref ?? "#"} label={actionLabel ?? ""} size="md" />
       {/if}
     </div>
   {/if}