feat: initial mono-repo with 30 vanity domain sites

Scaffold complete repo structure:
- 28 static sites extracted from running containers on mlake
- 2 dynamic sites (dasbes.de, dumusst.com) marked for separate handling
- Template system with 6 templates (person-dark/light, product-dark, editorial, fun, minimal)
- Shared CSS (variables, responsive, animations, noise overlay)
- nginx config generator with multi-domain alias support
- Build script with Docker-based nginx validation
- add-site.sh helper for scaffolding new domains
- Dockerfile for single nginx:alpine container

Sites: clemensplassmann.de, danosi.de, deinesei.de, derkaiseristnackt.de,
elefantenhor.de, fragina.de, frenchkis.de, ichbinaufbali.de, ichbinaufbarley.de,
insain.de, julietensity.de, kainco.de (+keinco.de), kainstress.de, keinefreun.de,
knzlmgmt.de, kopffrai.de, legalais.de, machesdocheinfach.de, mai-otto.de
(+otto.flexsiebels.de, ottomatisch.de, ichbinotto.de), martinsiebels.de,
matthiasbreier.de, osterai.de, paragraphenraiter.de, schulfrai.de, smartin3.de,
sorgenfrai.de, vonschraitter.de, wartebitte.de

Refs: otto#341

templates/minimal.html

@@ -0,0 +1,36 @@
+{{template_css_start}}
+    :root {
+      --bg: #0a0a0c;
+      --bg-elevated: #111115;
+      --text: #e8e8ed;
+      --text-dimmed: #6e6e7a;
+      --accent: {{accent}};
+      --font-primary: '{{font_primary}}', -apple-system, BlinkMacSystemFont, sans-serif;
+    }
+
+    .container {
+      display: flex;
+      flex-direction: column;
+      align-items: center;
+      justify-content: center;
+      min-height: 100vh;
+      text-align: center;
+    }
+
+    h1 {
+      font-size: 2rem;
+      font-weight: 600;
+      margin-bottom: var(--spacing-sm);
+    }
+
+    .subtitle {
+      color: var(--text-dimmed);
+      font-size: 1rem;
+    }
+{{template_css_end}}
+{{template_body_start}}
+    <div class="container fade-in">
+      <h1>{{title}}</h1>
+      <div class="subtitle">{{tagline}}</div>
+    </div>
+{{template_body_end}}