Add link editing, AI re-description, and footer

Links can now be edited manually (title, summary, category,
manufacturer, tags) via an inline edit form, with a "KI neu
beschreiben lassen" action that re-fetches the URL and lets the AI
regenerate all fields. Editing recomputes the search embedding.

Also adds an app footer showing author, version, and hostname.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/templates/_link_card.html

@@ -7,11 +7,17 @@
         {{ link.url }}
       </div>
     </div>
-    <button class="danger"
-            hx-delete="/links/{{ link.id }}"
-            hx-target="#link-{{ link.id }}"
-            hx-swap="outerHTML"
-            hx-confirm="Diesen Link wirklich löschen?">✕</button>
+    <div style="display:flex; gap:4px; flex-shrink:0;">
+      <button class="ghost" style="padding:4px 10px; font-size:.8rem;"
+              hx-get="/links/{{ link.id }}/edit"
+              hx-target="#link-{{ link.id }}"
+              hx-swap="outerHTML">✎ Bearbeiten</button>
+      <button class="danger"
+              hx-delete="/links/{{ link.id }}"
+              hx-target="#link-{{ link.id }}"
+              hx-swap="outerHTML"
+              hx-confirm="Diesen Link wirklich löschen?">✕</button>
+    </div>
   </div>
 
   {% if link.summary %}