Improve Active Workers table and recover stale tasks

Backend:
- Add _recover_stale_tasks() to reset tasks stuck in 'in_progress'
  from previous crashes (tasks >5 min old get reset to pending)
- Called automatically on startup

Frontend:
- Fix dark mode colors using CSS variables instead of hardcoded values
- Add elapsed time column showing how long task has been running
- Add spinning indicator next to package name
- Add status badge (Running/Stale?)
- Highlight stale tasks (>5 min) in amber
- Auto-updates every 5 seconds with existing refresh

frontend/src/pages/AdminJobsPage.css

@@ -280,14 +280,14 @@
   display: flex;
   align-items: center;
   gap: 0.5rem;
-  color: #3b82f6;
+  color: var(--color-primary, #3b82f6);
   margin-top: 1rem;
 }
 
 .pulse-indicator {
   width: 8px;
   height: 8px;
-  background-color: #3b82f6;
+  background-color: var(--color-primary, #3b82f6);
   border-radius: 50%;
   animation: pulse 1.5s ease-in-out infinite;
 }
@@ -304,21 +304,21 @@
 }
 
 .jobs-table.active-table {
-  border: 1px solid #3b82f6;
+  border: 1px solid var(--color-primary, #3b82f6);
   border-radius: 4px;
 }
 
 .jobs-table.active-table th {
-  background: #eff6ff;
-  color: #1d4ed8;
+  background: var(--bg-tertiary);
+  color: var(--color-primary, #3b82f6);
 }
 
 .jobs-table .active-row {
-  background-color: #f0f9ff;
+  background-color: var(--bg-secondary);
 }
 
 .jobs-table .active-row:hover {
-  background-color: #e0f2fe;
+  background-color: var(--bg-tertiary);
 }
 
 .jobs-table .version-constraint {
@@ -327,6 +327,66 @@
   color: var(--text-secondary);
 }
 
+/* Spinner for active tasks */
+.spinner {
+  display: inline-block;
+  width: 12px;
+  height: 12px;
+  border: 2px solid var(--border-color);
+  border-top-color: var(--color-primary, #3b82f6);
+  border-radius: 50%;
+  animation: spin 1s linear infinite;
+  margin-right: 0.5rem;
+  vertical-align: middle;
+}
+
+@keyframes spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
+/* Elapsed time */
+.elapsed-time {
+  font-family: monospace;
+  font-size: 0.9rem;
+  color: var(--text-secondary);
+}
+
+.elapsed-time.stale {
+  color: #f59e0b;
+  font-weight: 500;
+}
+
+/* Status badges */
+.status-badge {
+  display: inline-block;
+  padding: 0.2rem 0.5rem;
+  border-radius: 4px;
+  font-size: 0.75rem;
+  font-weight: 500;
+  text-transform: uppercase;
+}
+
+.status-badge.running {
+  background-color: rgba(59, 130, 246, 0.15);
+  color: var(--color-primary, #3b82f6);
+}
+
+.status-badge.stale {
+  background-color: rgba(245, 158, 11, 0.15);
+  color: #f59e0b;
+}
+
+/* Stale row highlighting */
+.jobs-table .stale-row {
+  background-color: rgba(245, 158, 11, 0.1);
+}
+
+.jobs-table .stale-row:hover {
+  background-color: rgba(245, 158, 11, 0.15);
+}
+
 /* Responsive */
 @media (max-width: 768px) {
   .status-cards {

frontend/src/pages/AdminJobsPage.tsx

@@ -212,25 +212,43 @@ function AdminJobsPage() {
                           <th>Version</th>
                           <th>Depth</th>
                           <th>Attempt</th>
-                          <th>Started</th>
+                          <th>Elapsed</th>
+                          <th>Status</th>
                         </tr>
                       </thead>
                       <tbody>
-                        {activeTasks.map((task) => (
-                          <tr key={task.id} className="active-row">
-                            <td className="package-name">{task.package}</td>
-                            <td className="version-constraint">
-                              {task.version_constraint || '*'}
-                            </td>
-                            <td>{task.depth}</td>
-                            <td>{task.attempts + 1}</td>
-                            <td className="timestamp">
-                              {task.started_at
-                                ? new Date(task.started_at).toLocaleTimeString()
-                                : '-'}
-                            </td>
-                          </tr>
-                        ))}
+                        {activeTasks.map((task) => {
+                          const elapsed = task.started_at
+                            ? Math.floor((Date.now() - new Date(task.started_at).getTime()) / 1000)
+                            : 0;
+                          const minutes = Math.floor(elapsed / 60);
+                          const seconds = elapsed % 60;
+                          const elapsedStr = minutes > 0
+                            ? `${minutes}m ${seconds}s`
+                            : `${seconds}s`;
+                          const isStale = elapsed > 300; // 5 minutes
+                          return (
+                            <tr key={task.id} className={`active-row ${isStale ? 'stale-row' : ''}`}>
+                              <td className="package-name">
+                                <span className="spinner"></span>
+                                {task.package}
+                              </td>
+                              <td className="version-constraint">
+                                {task.version_constraint || '*'}
+                              </td>
+                              <td>{task.depth}</td>
+                              <td>{task.attempts + 1}</td>
+                              <td className={`elapsed-time ${isStale ? 'stale' : ''}`}>
+                                {elapsedStr}
+                              </td>
+                              <td className="status-cell">
+                                <span className={`status-badge ${isStale ? 'stale' : 'running'}`}>
+                                  {isStale ? 'Stale?' : 'Running'}
+                                </span>
+                              </td>
+                            </tr>
+                          );
+                        })}
                       </tbody>
                     </table>
                   </div>