fix(gateway): install bedrock-realtime extra for Nova Sonic realtime (#34426)

The gateway image installed --extra proxy/proxy-runtime/extra_proxy/semantic-router
but not bedrock-realtime, so aws-sdk-bedrock-runtime was absent. Bedrock Nova Sonic
speech-to-speech uses InvokeModelWithBidirectionalStream (which boto3 cannot do) via
that package, so realtime requests failed at startup with 'Missing
aws_sdk_bedrock_runtime'. Add the extra to both uv sync stages; it is already in
uv.lock so --frozen resolves, and the package/marker (python>=3.12) matches the
python3.13 image.

gateway/Dockerfile

@@ -46,6 +46,7 @@ RUN --mount=type=cache,target=/root/.cache/uv \
         --extra proxy-runtime \
         --extra extra_proxy \
         --extra semantic-router \
+        --extra bedrock-realtime \
         --python python3
 
 # Stage 2 — copy source and install the project + workspace members.
@@ -57,6 +58,7 @@ RUN --mount=type=cache,target=/root/.cache/uv \
         --extra proxy-runtime \
         --extra extra_proxy \
         --extra semantic-router \
+        --extra bedrock-realtime \
         --python python3
 
 RUN mkdir -p /home/nonroot && \