tests: fix mypy type errors in security tests

app/api/routes.py

@@ -565,7 +565,7 @@ def is_trusted_proxy() -> bool:
     Result is cached per-request in Flask's g object for efficiency.
     """
     if hasattr(g, "_trusted_proxy"):
-        return g._trusted_proxy
+        return bool(g._trusted_proxy)
 
     expected = current_app.config.get("TRUSTED_PROXY_SECRET", "")
     if not expected:
@@ -573,7 +573,7 @@ def is_trusted_proxy() -> bool:
         return True
     provided = request.headers.get("X-Proxy-Secret", "")
     g._trusted_proxy = hmac.compare_digest(expected, provided)
-    return g._trusted_proxy
+    return bool(g._trusted_proxy)
 
 
 def get_client_fingerprint() -> str | None: