feat: progressive multi-round face matching + pending person API

- Identity agent: per-face max matching, multi-round with derived
  seeds from high-confidence faces, angle diversity filter (cosine sim < 0.90)
- Pending person API: POST /file/:file_uuid/pending-person
  + GET /file/:file_uuid/pending-persons with status=pending, source=manual
- Update API docs (07_identity.md)

src/worker/processor.rs

@@ -747,6 +747,27 @@ impl ProcessorPool {
                     pid: 0,
                 })
             }
+            ProcessorType::FaceCluster => {
+                let result = processor::process_face_cluster(
+                    video_path,
+                    output_path.to_str().unwrap(),
+                    uuid,
+                    Some(&sample_frames),
+                )
+                .await?;
+                tracing::info!(
+                    "FACE_CLUSTER completed, output: {}",
+                    output_path.to_str().unwrap()
+                );
+                Ok(ProcessorOutput {
+                    data: serde_json::to_value(result)?,
+                    chunks_produced: 0,
+                    frames_processed: 0,
+                    total_frames: 0,
+                    retry_count: 0,
+                    pid: 0,
+                })
+            }
             ProcessorType::Pose => {
                 let result = processor::process_pose(
                     video_path,