feat: standalone focus items with edit, convert, project tab, domain ordering

- Add standalone text line items to focus (quick-add with optional domain)
- Edit page for standalone items (title, domain, project)
- Convert standalone items to task, note, link, or list item
- Focus tab on project detail page showing assigned focus items
- Sort domain groups: General first, then by domain sort_order
- Add domain_id and title to nullable_fields in BaseRepository

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

templates/project_detail.html

@@ -40,6 +40,7 @@
     <a href="/projects/{{ item.id }}?tab=lists" class="tab-item {{ 'active' if tab == 'lists' }}">Lists{% if counts.lists %} ({{ counts.lists }}){% endif %}</a>
     <a href="/projects/{{ item.id }}?tab=decisions" class="tab-item {{ 'active' if tab == 'decisions' }}">Decisions{% if counts.decisions %} ({{ counts.decisions }}){% endif %}</a>
     <a href="/projects/{{ item.id }}?tab=meetings" class="tab-item {{ 'active' if tab == 'meetings' }}">Meetings{% if counts.meetings %} ({{ counts.meetings }}){% endif %}</a>
+    <a href="/projects/{{ item.id }}?tab=focus" class="tab-item {{ 'active' if tab == 'focus' }}">Focus{% if counts.focus %} ({{ counts.focus }}){% endif %}</a>
     <a href="/projects/{{ item.id }}?tab=processes" class="tab-item {{ 'active' if tab == 'processes' }}">Processes</a>
     <a href="/projects/{{ item.id }}?tab=contacts" class="tab-item {{ 'active' if tab == 'contacts' }}">Contacts{% if counts.contacts %} ({{ counts.contacts }}){% endif %}</a>
 </div>
@@ -162,6 +163,20 @@
 <div class="empty-state"><div class="empty-state-text">No meetings linked to this project</div></div>
 {% endfor %}
 
+{% elif tab == 'focus' %}
+{% for f in tab_data %}
+<div class="list-row">
+    <span class="row-title"><a href="/focus/{{ f.id }}/edit">{{ f.title }}</a></span>
+    {% if f.domain_name %}<span class="row-tag" style="{% if f.domain_color %}border-color:{{ f.domain_color }};color:{{ f.domain_color }}{% endif %}">{{ f.domain_name }}</span>{% endif %}
+    <span class="row-meta">{{ f.created_at.strftime('%Y-%m-%d') if f.created_at else '' }}</span>
+    <div class="row-actions">
+        <a href="/focus/{{ f.id }}/edit" class="btn btn-ghost btn-xs">Edit</a>
+    </div>
+</div>
+{% else %}
+<div class="empty-state"><div class="empty-state-text">No focus items assigned to this project</div></div>
+{% endfor %}
+
 {% elif tab == 'processes' %}
 <div class="empty-state"><div class="empty-state-text">Process management coming soon</div></div>