feat: add internal_component block type with contact form

InternalComponentBlock dispatches on `component` field value.
ContactFormComponent submits via /api/contact (SvelteKit proxy →
CMS /api/forms/kontakt/submit) with honeypot + client_age_ms.
BlockRenderer and block-types.ts updated accordingly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/components/blocks/InternalComponentBlock.svelte

@@ -0,0 +1,18 @@
+<script lang="ts">
+  import { getBlockLayoutClasses } from "$lib/block-layout";
+  import type { InternalComponentBlockData } from "$lib/block-types";
+  import ContactFormComponent from "$lib/components/internal/ContactFormComponent.svelte";
+
+  let { block }: { block: InternalComponentBlockData } = $props();
+
+  const layoutClasses = $derived(getBlockLayoutClasses(block.layout));
+  const component = $derived(block.component ?? "");
+</script>
+
+<div class={layoutClasses} data-block="InternalComponent" data-block-type="internal_component" data-block-slug={block._slug}>
+  {#if component === "form-contact"}
+    <ContactFormComponent />
+  {:else}
+    <p class="text-sm text-stein-500">Unbekannte interne Komponente: <code>{component}</code></p>
+  {/if}
+</div>