feat: add search_by_appearance agent tool for clothing color search

- New Python script: clothing_color_search.py
- New agent tool: search_by_appearance (red, blue, green, etc.)
- Uses appearance.json person bboxes + HSV color analysis
- Returns matched frames with confidence scores

src/api/agent_search.rs

@@ -276,6 +276,15 @@ fn make_tools(pool: &sqlx::PgPool) -> Vec<ToolDef> {
             }),
             vec!["file_uuid", "node_id"],
         ),
+        function_calling::make_tool(
+            "search_by_appearance",
+            "根據衣服顏色搜尋影片中的人物。支援顏色：red, orange, yellow, green, cyan, blue, purple, white, black。",
+            serde_json::json!({
+                "file_uuid": {"type": "string", "description": "影片 UUID"},
+                "color": {"type": "string", "description": "目標顏色: red, orange, yellow, green, cyan, blue, purple, white, black"}
+            }),
+            vec!["file_uuid", "color"],
+        ),
     ]
 }
 
@@ -310,6 +319,7 @@ async fn execute_tool(pool: &sqlx::PgPool, tool_call: &ToolCall) -> (String, Str
         "get_file_info" => tools::exec_get_file_info(pool, &args).await,
         "get_representative_frame" => tools::exec_get_representative_frame(pool, &args).await,
         "analyze_frame" => tools::exec_analyze_frame(pool, &args).await,
+        "search_by_appearance" => tools::exec_search_by_appearance(pool, &args).await,
         _ => Err(format!("Unknown tool: {}", name)),
     };
     let content = match result {