Replace internal todos with Vikunja API wrapper

- New app/vikunja.py: get_tasks, create_task, update_task, delete_task
- /todos page now reads from and writes to Vikunja (create, mark done, delete)
- Auto-todos (clean build plate, filament low) post to Vikunja after DB commit
- /api/todos router proxies to Vikunja
- .env.install: VIKUNJA_URL, VIKUNJA_API_TOKEN, VIKUNJA_PROJECT_ID

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

app/templates/todos.html

@@ -2,39 +2,63 @@
 {% block title %}To-Do — POPS{% endblock %}
 
 {% block content %}
-<h5 class="text-white mb-4">To-Do</h5>
+<div class="d-flex align-items-center justify-content-between mb-4">
+  <h5 class="text-white mb-0">To-Do</h5>
+</div>
+
+{# ── Add task ── #}
+<form method="POST" action="/todos" class="mb-3 d-flex gap-2" style="max-width:480px">
+  <input type="text" name="title" required
+         class="form-control form-control-sm bg-dark border-secondary text-white"
+         placeholder="New task…">
+  <button type="submit" class="btn btn-sm btn-primary px-3">Add</button>
+</form>
+
 <div class="card">
   {% if todos %}
-  <table class="table table-dark table-hover mb-0 align-middle">
+  <table class="table table-dark table-hover mb-0 align-middle" style="font-size:.875rem">
     <thead>
       <tr class="text-secondary small">
+        <th class="fw-normal" style="width:32px"></th>
         <th class="fw-normal">Task</th>
-        <th class="fw-normal">Printer</th>
-        <th class="fw-normal text-center">Done</th>
         <th class="fw-normal text-end">Created</th>
+        <th class="fw-normal" style="width:40px"></th>
       </tr>
     </thead>
     <tbody>
     {% for t in todos %}
-    <tr class="{% if t.done %}opacity-50{% endif %}">
-      <td class="{% if t.done %}text-decoration-line-through text-secondary{% else %}text-white{% endif %}">
-        {{ t.title }}
-      </td>
-      <td class="text-secondary small">{{ t.printer.name if t.printer else '—' }}</td>
-      <td class="text-center">
-        {% if t.done %}
+    {% set done = t.done %}
+    <tr class="{% if done %}opacity-50{% endif %}">
+      <td>
+        {% if done %}
           <i class="bi bi-check-circle-fill text-success"></i>
         {% else %}
-          <i class="bi bi-circle text-secondary"></i>
+        <form method="POST" action="/todos/{{ t.id }}/done" class="m-0">
+          <button type="submit" class="btn btn-link p-0 text-secondary" title="Mark done">
+            <i class="bi bi-circle"></i>
+          </button>
+        </form>
         {% endif %}
       </td>
-      <td class="text-secondary small text-end">{{ t.created_at.strftime('%d.%m.%Y') }}</td>
+      <td class="{% if done %}text-decoration-line-through text-secondary{% else %}text-white{% endif %}">
+        {{ t.title }}
+      </td>
+      <td class="text-secondary small text-end text-nowrap">
+        {{ t.created[:10] if t.created else '—' }}
+      </td>
+      <td>
+        <form method="POST" action="/todos/{{ t.id }}/delete" class="m-0 text-end">
+          <button type="submit" class="btn btn-link p-0 text-secondary" title="Delete">
+            <i class="bi bi-trash3"></i>
+          </button>
+        </form>
+      </td>
     </tr>
     {% endfor %}
     </tbody>
   </table>
   {% else %}
-  <div class="card-body text-secondary">No to-do items yet.</div>
+  <div class="card-body text-secondary">No tasks. Nice.</div>
   {% endif %}
 </div>
 {% endblock %}