feat: focus priority, focus links, task list assignment, lists drag-and-drop, URL display fixes

- Focus page: turn sequence number into persistent editable priority (focus_priority column)
- Focus detail: add links section (add existing, create new, unlink) via focus_links junction table
- Focus detail: add copy and inline edit for checklist items
- Task detail lists tab: add existing list assignment and unlink actions
- Lists page: add drag-and-drop reorder support
- Links/bookmarks pages: remove artificial URL truncation, use CSS ellipsis

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

templates/weblinks.html

@@ -64,9 +64,7 @@
                 <span class="row-title">
                     <a href="{{ item.url }}" target="_blank" rel="noopener">{{ item.label }}</a>
                 </span>
-                <span class="row-meta text-xs" style="max-width: 200px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;">
-                    {{ item.url }}
-                </span>
+                <span class="row-meta" style="min-width:0;overflow:hidden;text-overflow:ellipsis;">{{ item.url }}</span>
                 {% if item.tags %}
                 {% for tag in item.tags %}
                 <span class="row-tag">{{ tag }}</span>