Feature: HTMX + Jinja2 Frontend ersetzt Next.js komplett

- Kein Node.js, kein npm, kein Build-Schritt mehr
- HTMX 2.0.4 + PicoCSS 2 vendored in backend/static/
- Jinja2 Templates für alle 9 Seiten (Dashboard, ZFS, Snapshots,
  Shares, Identities, Logs, Services, Navigator, Login)
- HTMX Fragments für Live-Updates (30s Polling Dashboard)
- JWT als httpOnly Cookie statt localStorage
- Disk Usage zeigt TB/PB korrekt (Jinja2 serverseitig formatiert)
- Update-safe: nur Python-Deps, keine npm-Abhängigkeiten

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

backend/templates/fragments/navigator.html

@@ -0,0 +1,40 @@
+{% if error %}
+<p style="color:#fca5a5">&#9888; {{ error }}</p>
+{% else %}
+{% if parent_path %}
+<div style="margin-bottom:0.5rem">
+  <button class="outline secondary"
+          hx-get="/fragments/navigator?path={{ parent_path | urlencode }}"
+          hx-target="#nav-content"
+          hx-swap="innerHTML">&#8593; Übergeordnet</button>
+  <span style="font-family:monospace;margin-left:0.5rem;color:var(--pico-muted-color)">{{ current_path }}</span>
+</div>
+{% endif %}
+<table>
+  <thead><tr><th>Name</th><th>Typ</th><th>Größe</th><th>Geändert</th></tr></thead>
+  <tbody>
+  {% for item in items %}
+  <tr>
+    <td>
+      {% if item.type == 'directory' %}
+      <button class="outline secondary" style="padding:0.1rem 0.4rem;font-size:0.85rem"
+              hx-get="/fragments/navigator?path={{ item.path | urlencode }}"
+              hx-target="#nav-content"
+              hx-swap="innerHTML">
+        &#128193; {{ item.name }}
+      </button>
+      {% else %}
+      <span style="font-family:monospace;font-size:0.85rem">&#128196; {{ item.name }}</span>
+      {% endif %}
+    </td>
+    <td><span class="badge">{{ item.type }}</span></td>
+    <td style="font-size:0.85rem">{{ item.size }}</td>
+    <td style="font-size:0.8rem;color:var(--pico-muted-color)">{{ item.modified }}</td>
+  </tr>
+  {% endfor %}
+  </tbody>
+</table>
+{% if not items %}
+<p style="color:var(--pico-muted-color)">Verzeichnis ist leer.</p>
+{% endif %}
+{% endif %}