refactor: remove face embedding architecture - single Qdrant _faces collection

- Delete FaceEmbeddingDb module (face_embedding_db.rs)
- Stub match_faces_iterative, generate_seed_embeddings, tmdb_match_handler
- Remove sync_trace_embeddings, populate_face_embeddings_to_qdrant
- Remove embedding from face.json output (face_processor.py)
- Remove embedding from PG UPDATE (store_traced_faces.py)
- Remove workspace traces staging (checkin.rs, qdrant_workspace.rs)
- Fix tests: add pose_angle to Face, hand_nodes to TkgResult

Disabled functions (need reimplement with _faces):
- match_faces_iterative (identity agent)
- generate_seed_embeddings (TMDb seeds)
- tmdb_match_handler (TMDb matching)
- cluster_face_embeddings, search_similar_faces
- merge_traces_within_cuts

src/core/checkin.rs

@@ -145,42 +145,6 @@ pub async fn checkin(db: &PostgresDb, file_uuid: &str) -> Result<CheckinResult>
                     }
                 }
             }
-
-            // Traces → production traces collection
-            let traces_coll = format!(
-                "{}_traces",
-                crate::core::config::REDIS_KEY_PREFIX
-                    .as_str()
-                    .trim_end_matches(':')
-            );
-            for point in &ws_data.traces {
-                if let Some(ref vector) = point.vector {
-                    let payload_val: serde_json::Value =
-                        serde_json::to_value(&point.payload).unwrap_or(serde_json::Value::Null);
-                    let point_id: u64 = match point.id.parse::<u64>() {
-                        Ok(id) => id,
-                        Err(_) => {
-                            use std::hash::{Hash, Hasher};
-                            let mut hasher = std::collections::hash_map::DefaultHasher::new();
-                            point.id.hash(&mut hasher);
-                            hasher.finish()
-                        }
-                    };
-                    if let Err(e) = qdrant
-                        .upsert_vector_to_collection(
-                            &traces_coll,
-                            point_id,
-                            vector,
-                            Some(payload_val),
-                        )
-                        .await
-                    {
-                        warn!("Failed to checkin trace vector {}: {}", point.id, e);
-                    } else {
-                        vectors_moved += 1;
-                    }
-                }
-            }
         }
         Err(e) => {
             warn!("Failed to scroll Qdrant workspace for {}: {}", file_uuid, e);
@@ -297,10 +261,9 @@ pub async fn checkout(db: &PostgresDb, file_uuid: &str) -> Result<CheckoutResult
     let prefix = crate::core::config::REDIS_KEY_PREFIX
         .as_str()
         .trim_end_matches(':');
-    let traces_coll = format!("{}_traces", prefix);
     let voice_coll = format!("{}_voice", file_uuid);
 
-    for coll in &[traces_coll, voice_coll] {
+    for coll in &[voice_coll] {
         if let Err(e) = QdrantDb::delete_by_uuid_from_collection(
             &qdrant.client,
             &qdrant.base_url,