Bump httpx to >=0.28.1 to satisfy openenv-core 0.2.2+

The Space build failed: openenv-core 0.2.x now requires httpx>=0.28.1
but we pinned httpx==0.27.2. 0.28 is API-compatible for our TestClient
usage and the OpenSOCClient.

Made-with: Cursor

pyproject.toml

@@ -11,7 +11,7 @@ dependencies = [
     "uvicorn[standard]==0.32.1",
     "pydantic==2.10.3",
     "requests==2.32.3",
-    "httpx==0.27.2",
+    "httpx>=0.28.1,<0.29",
     "openenv-core>=0.2.0",
     "pyyaml==6.0.2",
     "gradio>=4.40,<5",

requirements.txt

@@ -2,7 +2,7 @@ fastapi==0.115.5
 uvicorn[standard]==0.32.1
 pydantic==2.10.3
 requests==2.32.3
-httpx==0.27.2
+httpx>=0.28.1,<0.29
 openenv-core>=0.2.0
 pyyaml==6.0.2
 gradio>=4.40,<5