feat: update core API, database layer, and worker modules

- Remove unused imports (n8n_search, universal_search, Client, Arc, etc.)
- Update API endpoints for identity, face recognition, search
- Fix postgres_db.rs search_videos parent_uuid column
- Add snapshot API and identity agent API
- Clean up backup files (.bak, .bak2)

src/core/person_identity.rs

@@ -12,7 +12,7 @@ pub struct PersonIdentity {
     pub person_id: String,
     pub face_identity_id: Option<i32>,
     pub speaker_id: Option<String>,
-    pub video_uuid: String,
+    pub file_uuid: String,
     pub confidence: f64,
     pub name: Option<String>,
     pub metadata: serde_json::Value,
@@ -85,7 +85,7 @@ pub struct SuggestedBinding {
 pub struct PersonAppearance {
     pub id: i32,
     pub person_id: String,
-    pub video_uuid: String,
+    pub file_uuid: String,
     pub start_time: f64,
     pub end_time: f64,
     pub duration: f64,
@@ -124,7 +124,7 @@ pub struct PersonStatistics {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CreatePersonIdentityRequest {
-    pub video_uuid: String,
+    pub file_uuid: String,
     pub face_identity_id: Option<i32>,
     pub speaker_id: Option<String>,
     pub name: Option<String>,
@@ -196,7 +196,7 @@ mod tests {
             person_id: "person_001".to_string(),
             face_identity_id: Some(123),
             speaker_id: Some("SPEAKER_00".to_string()),
-            video_uuid: "video_abc".to_string(),
+            file_uuid: "video_abc".to_string(),
             confidence: 0.85,
             name: Some("张三".to_string()),
             metadata: serde_json::json!({"role": "host"}),
@@ -220,7 +220,7 @@ mod tests {
         let appearance = PersonAppearance {
             id: 1,
             person_id: "person_001".to_string(),
-            video_uuid: "video_abc".to_string(),
+            file_uuid: "video_abc".to_string(),
             start_time: 10.5,
             end_time: 25.3,
             duration: 14.8,