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/task_detail.html

@@ -133,11 +133,31 @@
 {% endfor %}
 
 {% elif tab == 'lists' %}
-<a href="/lists/create?task_id={{ item.id }}&domain_id={{ item.domain_id }}" class="btn btn-ghost btn-sm mb-3">+ New List</a>
+<div class="card mb-3">
+    <form action="/tasks/{{ item.id }}/lists/add" method="post" class="flex gap-2 items-end" style="padding: 12px;">
+        <div class="form-group" style="flex:1; margin:0;">
+            <label class="form-label">Add Existing List</label>
+            <select name="list_id" class="form-select" required>
+                <option value="">Select list...</option>
+                {% for l in all_lists %}
+                <option value="{{ l.id }}">{{ l.name }}</option>
+                {% endfor %}
+            </select>
+        </div>
+        <button type="submit" class="btn btn-primary btn-sm">Add</button>
+        <a href="/lists/create?task_id={{ item.id }}&domain_id={{ item.domain_id }}" class="btn btn-ghost btn-sm">+ New List</a>
+    </form>
+</div>
 {% for l in tab_data %}
 <div class="list-row">
     <span class="row-title"><a href="/lists/{{ l.id }}">{{ l.name }}</a></span>
     <span class="row-meta">{{ l.item_count }} items</span>
+    <div class="row-actions">
+        <a href="/lists/{{ l.id }}/edit" class="btn btn-ghost btn-xs">Edit</a>
+        <form action="/tasks/{{ item.id }}/lists/{{ l.id }}/remove" method="post" style="display:inline">
+            <button class="btn btn-ghost btn-xs" title="Unlink">Unlink</button>
+        </form>
+    </div>
 </div>
 {% else %}
 <div class="empty-state"><div class="empty-state-text">No lists linked to this task</div></div>