Add priority flag to jobs

- Migration 0010: priority BOOLEAN NOT NULL DEFAULT 0 on print_jobs
- Priority jobs sort above normal jobs in the list
- Checkbox in Add Job modal; warning icon in list; badge on detail page

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

app/templates/job_detail.html

@@ -10,6 +10,7 @@
     <div class="d-flex align-items-center gap-2">
       <h5 class="text-white mb-0">{{ job.file_name or job.name }}</h5>
       {% set s = job.status.value %}
+      {% if job.priority %}<span class="badge bg-warning text-dark"><i class="bi bi-exclamation-circle me-1"></i>Priority</span>{% endif %}
       {% 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>