feat: Auto-retry tasks, 403 proxy rotation, task deletion

- Fix 403 handler to rotate BOTH proxy and fingerprint (was only fingerprint)
- Add auto-retry logic to task service (retry up to max_retries before failing)
- Add error tooltip on task status badge showing retry count and error message
- Add DELETE /api/tasks/:id endpoint (only for non-running tasks)
- Add delete button to JobQueue task table

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

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

backend/src/tasks/task-service.ts

@@ -206,15 +206,53 @@ class TaskService {
   }
 
   /**
-   * Mark a task as failed
+   * Mark a task as failed, with auto-retry if under max_retries
+   * Returns true if task was re-queued for retry, false if permanently failed
    */
-  async failTask(taskId: number, errorMessage: string): Promise<void> {
+  async failTask(taskId: number, errorMessage: string): Promise<boolean> {
+    // Get current retry state
+    const result = await pool.query(
+      `SELECT retry_count, max_retries FROM worker_tasks WHERE id = $1`,
+      [taskId]
+    );
+
+    if (result.rows.length === 0) {
+      return false;
+    }
+
+    const { retry_count, max_retries } = result.rows[0];
+    const newRetryCount = (retry_count || 0) + 1;
+
+    if (newRetryCount < (max_retries || 3)) {
+      // Re-queue for retry - reset to pending with incremented retry_count
+      await pool.query(
+        `UPDATE worker_tasks
+         SET status = 'pending',
+             worker_id = NULL,
+             claimed_at = NULL,
+             started_at = NULL,
+             retry_count = $2,
+             error_message = $3,
+             updated_at = NOW()
+         WHERE id = $1`,
+        [taskId, newRetryCount, `Retry ${newRetryCount}: ${errorMessage}`]
+      );
+      console.log(`[TaskService] Task ${taskId} queued for retry ${newRetryCount}/${max_retries || 3}`);
+      return true;
+    }
+
+    // Max retries exceeded - mark as permanently failed
     await pool.query(
       `UPDATE worker_tasks
-       SET status = 'failed', completed_at = NOW(), error_message = $2
+       SET status = 'failed',
+           completed_at = NOW(),
+           retry_count = $2,
+           error_message = $3
        WHERE id = $1`,
-      [taskId, errorMessage]
+      [taskId, newRetryCount, `Failed after ${newRetryCount} attempts: ${errorMessage}`]
     );
+    console.log(`[TaskService] Task ${taskId} permanently failed after ${newRetryCount} attempts`);
+    return false;
   }
 
   /**