chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/sse_starlette/event.py

@@ -0,0 +1,96 @@
+import io
+import re
+import json
+from typing import Optional, Any, Union
+
+
+class ServerSentEvent:
+    """
+    Helper class to format data for Server-Sent Events (SSE).
+    """
+
+    _LINE_SEP_EXPR = re.compile(r"\r\n|\r|\n")
+    DEFAULT_SEPARATOR = "\r\n"
+
+    def __init__(
+        self,
+        data: Optional[Any] = None,
+        *,
+        event: Optional[str] = None,
+        id: Optional[str] = None,
+        retry: Optional[int] = None,
+        comment: Optional[str] = None,
+        sep: Optional[str] = None,
+    ) -> None:
+        self.data = data
+        self.event = event
+        self.id = id
+        self.retry = retry
+        self.comment = comment
+        self._sep = sep if sep is not None else self.DEFAULT_SEPARATOR
+
+    def encode(self) -> bytes:
+        buffer = io.StringIO()
+        if self.comment is not None:
+            for chunk in self._LINE_SEP_EXPR.split(str(self.comment)):
+                buffer.write(f": {chunk}{self._sep}")
+
+        if self.id is not None:
+            # Clean newlines in the event id
+            buffer.write("id: " + self._LINE_SEP_EXPR.sub("", self.id) + self._sep)
+
+        if self.event is not None:
+            # Clean newlines in the event name
+            buffer.write(
+                "event: " + self._LINE_SEP_EXPR.sub("", self.event) + self._sep
+            )
+
+        if self.data is not None:
+            # Break multi-line data into multiple data: lines
+            for chunk in self._LINE_SEP_EXPR.split(str(self.data)):
+                buffer.write(f"data: {chunk}{self._sep}")
+
+        if self.retry is not None:
+            if not isinstance(self.retry, int):
+                raise TypeError("retry argument must be int")
+            buffer.write(f"retry: {self.retry}{self._sep}")
+
+        buffer.write(self._sep)
+        return buffer.getvalue().encode("utf-8")
+
+
+class JSONServerSentEvent(ServerSentEvent):
+    """
+    Helper class to format JSON data for Server-Sent Events (SSE).
+    """
+
+    def __init__(
+        self,
+        data: Optional[Any] = None,
+        *args,
+        **kwargs,
+    ) -> None:
+        super().__init__(
+            json.dumps(
+                data,
+                ensure_ascii=False,
+                allow_nan=False,
+                indent=None,
+                separators=(",", ":"),
+            )
+            if data is not None
+            else None,
+            *args,
+            **kwargs,
+        )
+
+
+def ensure_bytes(data: Union[bytes, dict, ServerSentEvent, Any], sep: str) -> bytes:
+    if isinstance(data, bytes):
+        return data
+    if isinstance(data, ServerSentEvent):
+        return data.encode()
+    if isinstance(data, dict):
+        data["sep"] = sep
+        return ServerSentEvent(**data).encode()
+    return ServerSentEvent(str(data), sep=sep).encode()