feat(ui): drag-to-reorder sidebar projects with persistent order

Add drag-and-drop reordering to sidebar project list using dnd-kit,
persisted per-user via localStorage. Use consistent project order in
issue properties, new issue dialog, and issue detail mention options.
Move projects section below Work section in sidebar.

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

ui/src/components/Sidebar.tsx

@@ -88,13 +88,13 @@ export function Sidebar() {
             />
           </div>
 
-          <SidebarProjects />
-
           <SidebarSection label="Work">
             <SidebarNavItem to="/issues" label="Issues" icon={CircleDot} />
             <SidebarNavItem to="/goals" label="Goals" icon={Target} />
           </SidebarSection>
 
+          <SidebarProjects />
+
           <SidebarAgents />
 
           <SidebarSection label="Company">