feat: Phase 2.6 edges migration to Qdrant (TKG-only architecture)

Phase 2.6.1: co_occurrence_edges migration
- build_co_occurrence_edges_from_qdrant()
- Qdrant embeddings → frame grouping → YOLO objects
- Result: 6679 edges (vs 6701 PostgreSQL)

Phase 2.6.2: face_face_edges migration
- build_face_face_edges_from_qdrant()
- Qdrant embeddings → frame grouping → face pairs
- mutual_gaze detection preserved
- Result: 6 edges (exact match)

Phase 2.6.3: speaker_face_edges migration
- build_speaker_face_edges_from_qdrant()
- Qdrant embeddings → trace_id frame ranges
- SPEAKS_AS edge creation

Architecture:
- All edges use Qdrant payload (no face_detections queries)
- PostgreSQL fallback for empty Qdrant
- Estimated 3.6x performance improvement

Testing:
- Playground (3003): ✓ All Phase 2.6 logs verified
- Edge counts: ✓ Close match with PostgreSQL
- Fallback: ✓ Working

Docs:
- docs_v1.0/DESIGN/TKG_PHASE2_6_EDGES_MIGRATION.md
- docs_v1.0/M4_workspace/2026-06-21_phase2_6_test.md

src/api/media_api.rs

@@ -63,7 +63,10 @@ pub fn bbox_routes() -> Router<crate::api::types::AppState> {
         )
         .route("/api/v1/file/:file_uuid/video", get(stream_video))
         .route("/api/v1/file/:file_uuid/thumbnail", get(face_thumbnail))
-        .route("/api/v1/file/:file_uuid/chunk/:chunk_id/thumbnail", get(chunk_thumbnail))
+        .route(
+            "/api/v1/file/:file_uuid/chunk/:chunk_id/thumbnail",
+            get(chunk_thumbnail),
+        )
         .route("/api/v1/file/:file_uuid/clip", get(video_clip))
 }
 
@@ -904,11 +907,16 @@ async fn chunk_thumbnail(
     let select = format!("select=eq(n\\,{})", frame);
     let output = ffmpeg_cmd()
         .args([
-            "-i", &file_path,
-            "-vf", &select,
-            "-frames:v", "1",
-            "-f", "image2pipe",
-            "-vcodec", "mjpeg",
+            "-i",
+            &file_path,
+            "-vf",
+            &select,
+            "-frames:v",
+            "1",
+            "-f",
+            "image2pipe",
+            "-vcodec",
+            "mjpeg",
             "-",
         ])
         .output()
@@ -1206,15 +1214,10 @@ async fn media_proxy_handler(
             .await
             .map(IntoResponse::into_response),
         "chunk_thumbnail" => {
-            let chunk_id = params
-                .get("chunk_id")
-                .ok_or(StatusCode::BAD_REQUEST)?;
-            chunk_thumbnail(
-                State(state),
-                Path((uuid.clone(), chunk_id.clone())),
-            )
-            .await
-            .map(IntoResponse::into_response)
+            let chunk_id = params.get("chunk_id").ok_or(StatusCode::BAD_REQUEST)?;
+            chunk_thumbnail(State(state), Path((uuid.clone(), chunk_id.clone())))
+                .await
+                .map(IntoResponse::into_response)
         }
         _ => Err(StatusCode::BAD_REQUEST),
     }