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/quick_stats.html

@@ -0,0 +1,40 @@
+{% macro fmt_bytes(b) %}
+  {%- if b == 0 %}0 B
+  {%- elif b < 1024 %}{{ b }} B
+  {%- elif b < 1048576 %}{{ "%.1f"|format(b/1024) }} KB
+  {%- elif b < 1073741824 %}{{ "%.1f"|format(b/1048576) }} MB
+  {%- elif b < 1099511627776 %}{{ "%.1f"|format(b/1073741824) }} GB
+  {%- else %}{{ "%.1f"|format(b/1099511627776) }} TB
+  {%- endif %}
+{%- endmacro %}
+
+<div class="stat-card">
+  <h3>CPU Load</h3>
+  <p class="value">{{ cpu.load_average[0] if cpu.load_average else '–' }}</p>
+  <small>{{ cpu.count }} Kerne</small>
+</div>
+
+<div class="stat-card">
+  <h3>RAM</h3>
+  <p class="value">{{ fmt_bytes(mem.used) }}</p>
+  <small>von {{ fmt_bytes(mem.total) }}</small>
+  {% set pct = (mem.used / mem.total * 100)|int if mem.total else 0 %}
+  <div class="progress-bar-wrap" style="margin-top:0.4rem">
+    <div class="progress-bar {% if pct > 85 %}bar-red{% elif pct > 70 %}bar-yellow{% else %}bar-blue{% endif %}" style="width:{{ pct }}%"></div>
+  </div>
+</div>
+
+<div class="stat-card">
+  <h3>Uptime</h3>
+  <p class="value">{{ uptime.uptime_string if uptime else '–' }}</p>
+</div>
+
+<div class="stat-card">
+  <h3>Pools</h3>
+  <p class="value">{{ pools|length }}</p>
+  <small>
+    {% for p in pools %}
+      <span class="badge {% if p.health == 'ONLINE' %}badge-green{% elif p.health == 'DEGRADED' %}badge-yellow{% else %}badge-red{% endif %}">{{ p.name }}</span>
+    {% endfor %}
+  </small>
+</div>