Add Jinja2 web UI with Bootstrap 5 dark theme

- app/templates/: base layout with sidebar nav + 6 pages
  (dashboard, printers, jobs, filaments, todos, pricing)
- app/routers/ui.py: HTML routes querying the DB live
- API routes moved to /api/* prefix
- requirements: jinja2, python-multipart

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

app/templates/jobs.html

@@ -0,0 +1,52 @@
+{% extends "base.html" %}
+{% block title %}Jobs — POPS{% endblock %}
+
+{% block content %}
+<h5 class="text-white mb-4">Print Jobs</h5>
+<div class="card">
+  {% if jobs %}
+  <table class="table table-dark table-hover mb-0 align-middle">
+    <thead>
+      <tr class="text-secondary small">
+        <th class="fw-normal">Name</th>
+        <th class="fw-normal">Printer</th>
+        <th class="fw-normal">Filament</th>
+        <th class="fw-normal">Status</th>
+        <th class="fw-normal">Duration</th>
+        <th class="fw-normal text-end">Cost</th>
+        <th class="fw-normal text-end">Created</th>
+      </tr>
+    </thead>
+    <tbody>
+    {% for j in jobs %}
+    <tr>
+      <td class="fw-medium text-white">{{ j.name }}</td>
+      <td class="text-secondary small">{{ j.printer.name if j.printer else '—' }}</td>
+      <td class="text-secondary small">
+        {% if j.filament %}{{ j.filament.material.value }} {{ j.filament.color or '' }}{% else %}—{% endif %}
+      </td>
+      <td>
+        {% set s = j.status.value %}
+        {% if   s == 'printing'  %}<span class="badge bg-primary">printing</span>
+        {% elif s == 'done'      %}<span class="badge bg-success">done</span>
+        {% elif s == 'failed'    %}<span class="badge bg-danger">failed</span>
+        {% elif s == 'cancelled' %}<span class="badge bg-warning text-dark">cancelled</span>
+        {% else                  %}<span class="badge bg-secondary">queued</span>
+        {% endif %}
+      </td>
+      <td class="text-secondary small">
+        {% if j.duration_minutes %}{{ j.duration_minutes }} min{% else %}—{% endif %}
+      </td>
+      <td class="text-secondary small text-end">
+        {% if j.cost_eur %}€ {{ "%.2f"|format(j.cost_eur) }}{% else %}—{% endif %}
+      </td>
+      <td class="text-secondary small text-end">{{ j.created_at.strftime('%d.%m %H:%M') }}</td>
+    </tr>
+    {% endfor %}
+    </tbody>
+  </table>
+  {% else %}
+  <div class="card-body text-secondary">No jobs yet.</div>
+  {% endif %}
+</div>
+{% endblock %}