fix backend python compatibility

backend/app.py

@@ -7,7 +7,7 @@ import sqlite3
 from contextlib import contextmanager
 from datetime import datetime, timedelta, timezone
 from pathlib import Path
-from typing import Any
+from typing import Any, Dict, List
 from uuid import uuid4
 
 from fastapi import FastAPI, HTTPException, Request
@@ -33,7 +33,7 @@ app.add_middleware(
     allow_headers=["Content-Type"],
 )
 
-rate_bucket: dict[str, list[datetime]] = {}
+rate_bucket: Dict[str, List[datetime]] = {}
 
 
 class ShareCreateRequest(BaseModel):
@@ -146,7 +146,7 @@ def startup() -> None:
 
 
 @app.post("/api/share", response_model=ShareCreateResponse)
-def create_share(payload: ShareCreateRequest, request: Request) -> dict[str, str]:
+def create_share(payload: ShareCreateRequest, request: Request) -> Dict[str, str]:
     cleanup_expired()
     assert_rate_limit(request)
     if decoded_size(payload.ciphertext) > MAX_PAYLOAD_BYTES:
@@ -169,7 +169,7 @@ def create_share(payload: ShareCreateRequest, request: Request) -> dict[str, str
 
 
 @app.get("/api/share/{export_id}")
-def get_share(export_id: str) -> dict[str, Any]:
+def get_share(export_id: str) -> Dict[str, Any]:
     cleanup_expired()
     with connect() as db:
         row = db.execute("SELECT * FROM active_shares WHERE export_id = ?", (export_id,)).fetchone()
@@ -191,7 +191,7 @@ def get_share(export_id: str) -> dict[str, Any]:
 
 
 @app.post("/api/share/{export_id}/confirm-import")
-def confirm_import(export_id: str) -> dict[str, str]:
+def confirm_import(export_id: str) -> Dict[str, str]:
     cleanup_expired()
     with connect() as db:
         row = db.execute("SELECT export_id, created_at FROM active_shares WHERE export_id = ?", (export_id,)).fetchone()