feat: add task type hierarchy with subtypes in UI

src/pages/IssuesPage.tsx

@@ -49,7 +49,7 @@ export default function IssuesPage() {
 
       <table className="issues-table">
         <thead>
-          <tr><th>#</th><th>Title</th><th>Status</th><th>Priority</th><th>Type</th><th>Tags</th><th>Created</th></tr>
+          <tr><th>#</th><th>Title</th><th>Status</th><th>Priority</th><th>Type</th><th>Subtype</th><th>Tags</th><th>Created</th></tr>
         </thead>
         <tbody>
           {issues.map((i) => (
@@ -58,7 +58,7 @@ export default function IssuesPage() {
               <td className="issue-title">{i.title}</td>
               <td><span className="badge" style={{ backgroundColor: statusColors[i.status] || '#ccc' }}>{i.status}</span></td>
               <td><span className={`badge priority-${i.priority}`}>{i.priority}</span></td>
-              <td>{i.issue_type}</td>
+              <td>{i.issue_type}</td><td>{i.issue_subtype || "-"}</td>
               <td>{i.tags || '-'}</td>
               <td>{new Date(i.created_at).toLocaleDateString()}</td>
             </tr>