feat: i18n annotations — data-de/data-en + toggle for all 54 custom sites

Phase 2 of i18n rollout:
- All 54 static custom sites now have data-de/data-en attributes on
  visible text elements with English translations
- i18n.js script tag injected into all sites
- Language toggle button with machine-translation disclaimer added
  to every site's footer area
- Brand names / domain wordplay preserved unchanged in both languages
- 2 dynamic sites (dasbes.de, dumusst.com) skipped — no static HTML

sites/clemensplassmann.de/index.html

@@ -119,13 +119,18 @@
     <div class="container">
         <h1 class="name">Clemens Plassmann</h1>
         <div class="divider"></div>
-        <p class="title">Patent Litigation</p>
-        <p class="firm">Hogan Lovells</p>
+        <p class="title" data-de="Patent Litigation" data-en="Patent Litigation">Patent Litigation</p>
+        <p class="firm" data-de="Hogan Lovells" data-en="Hogan Lovells">Hogan Lovells</p>
         <div class="links">
-            <a href="https://www.hoganlovells.com/en/clemens-plassmann" target="_blank">Profile</a>
-            <a href="https://www.linkedin.com/in/clemens-plassmann/" target="_blank">LinkedIn</a>
+            <a href="https://www.hoganlovells.com/en/clemens-plassmann" target="_blank" data-de="Profil" data-en="Profile">Profile</a>
+            <a href="https://www.linkedin.com/in/clemens-plassmann/" target="_blank" data-de="LinkedIn" data-en="LinkedIn">LinkedIn</a>
+        </div>
+        <p class="footer" data-de="Erstellt von &lt;a href=&quot;https://flexsiebels.de&quot;&gt;Otto&lt;/a&gt;" data-en="Built by &lt;a href=&quot;https://flexsiebels.de&quot;&gt;Otto&lt;/a&gt;">Built by <a href="https://flexsiebels.de">Otto</a></p>
+        <div style="text-align:center;margin-top:16px;">
+          <button data-i18n-toggle title="Maschinell übersetzt / Machine-translated — German is the original." style="background:none;border:1px solid var(--text-muted,#444);color:var(--text-muted,#444);font-size:0.65rem;letter-spacing:0.1em;padding:4px 12px;border-radius:4px;cursor:pointer;">EN</button>
+          <br><small data-de="Maschinell übersetzt" data-en="Machine-translated" style="color:var(--text-muted,#444);font-size:0.6rem;opacity:0.5;">Maschinell übersetzt</small>
         </div>
-        <p class="footer">Built by <a href="https://flexsiebels.de">Otto</a></p>
     </div>
+  <script src="/shared/i18n.js"></script>
 </body>
 </html>