feat: switch frontend indexing to code-first identifiers

src/pages/DashboardPage.tsx

@@ -1,4 +1,5 @@
 import { useState, useEffect } from 'react'
+import { Link } from 'react-router-dom'
 import api from '@/services/api'
 import type { DashboardStats, Task } from '@/types'
 
@@ -60,8 +61,8 @@ export default function DashboardPage() {
           <tbody>
             {(stats.recent_tasks || []).map((i) => (
               <tr key={i.id}>
-                <td>{i.task_code || `#${i.id}`}</td>
-                <td><a href={`/tasks/${i.task_code || i.id}`}>{i.title}</a></td>
+                <td>{i.task_code || '—'}</td>
+                <td>{i.task_code ? <Link to={`/tasks/${i.task_code}`}>{i.title}</Link> : i.title}</td>
                 <td><span className={`badge status-${i.status}`}>{i.status}</span></td>
                 <td><span className={`badge priority-${i.priority}`}>{i.priority}</span></td>
                 <td>{i.task_type}</td><td>{i.task_subtype || "-"}</td>