feat: Add POST /api/tasks/fix-null-methods endpoint

Updates null method tasks to 'http' for proper worker qualification

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/routes/tasks.ts

@@ -891,6 +891,35 @@ router.post('/retry-failed', async (req: Request, res: Response) => {
   }
 });
 
+/**
+ * POST /api/tasks/fix-null-methods
+ * Update tasks with method=null to method='http'
+ * Ensures only HTTP-preflight workers can claim crawl tasks
+ */
+router.post('/fix-null-methods', async (_req: Request, res: Response) => {
+  try {
+    const { rows } = await pool.query(`
+      UPDATE worker_tasks
+      SET method = 'http', updated_at = NOW()
+      WHERE method IS NULL
+        AND role IN ('product_discovery', 'product_refresh', 'entry_point_discovery', 'store_discovery', 'payload_fetch')
+        AND status IN ('pending', 'failed')
+      RETURNING id, role, status
+    `);
+
+    console.log(`[Tasks] Fixed ${rows.length} tasks with null method → http`);
+
+    res.json({
+      success: true,
+      tasks_fixed: rows.length,
+      tasks: rows.slice(0, 20),
+    });
+  } catch (error: unknown) {
+    console.error('Error fixing null methods:', error);
+    res.status(500).json({ error: 'Failed to fix null methods' });
+  }
+});
+
 /**
  * GET /api/tasks/role/:role/last-completion
  * Get the last completion time for a role