fix: add .venv/bin to PATH in container Dockerfile (#471)

uv sync ignores UV_SYSTEM_PYTHON=1 and always creates a .venv directory,
so console scripts like opentelemetry-instrument are installed to
/app/.venv/bin/ which is not on PATH. This causes container startup to
fail with 'executable file not found in $PATH'.

Author: aidandaly24

src/assets/container/python/Dockerfile

@@ -11,7 +11,8 @@ ENV UV_SYSTEM_PYTHON=1 \
     PYTHONUNBUFFERED=1 \
     DOCKER_CONTAINER=1 \
     UV_DEFAULT_INDEX=${UV_DEFAULT_INDEX} \
-    UV_INDEX=${UV_INDEX}
+    UV_INDEX=${UV_INDEX} \
+    PATH="/app/.venv/bin:$PATH"
 
 RUN useradd -m -u 1000 bedrock_agentcore