fix: Safety in starter (#2731)

- fireworks, together do not support Llama-guard 3 8b model anymore 
- Need to default to ollama 
- current safety shields logic was not correct since the shield_id was
the provider ( which had duplicates )
- Followed similar logic to models 

Note: Seems a bit over-engineered but this can now be extended to other
providers and fits in the overall mechanism of how env_vars are used to
manage starter.

### How to test 
```
ENABLE_OLLAMA=ollama ENABLE_FIREWORKS=fireworks SAFETY_MODEL=llama-guard3:1b pytest -s -v tests/integration/ --stack-config starter -k 'not(supervised_fine_tune or builtin_tool_code or safety_with_image or code_interpreter_for or rag_and_code or truncation or register_and_unregister)' --text-model fireworks/meta-llama/Llama-3.3-70B-Instruct --vision-model fireworks/meta-llama/Llama-4-Scout-17B-16E-Instruct --safety-shield llama-guard3:1b --embedding-model all-MiniLM-L6-v2
```

### Related but not obvious in this PR 
In the llama-stack-ops repo, we run tests before publishing packages and
docker containers.
The actions in that repo were using the fireworks / together distros (
which are non-existent )

So need to update that to run with `starter` and use `ollama`
specifically for safety.

.github/workflows/integration-tests.yml

@@ -89,7 +89,7 @@ jobs:
             -k "not(builtin_tool or safety_with_image or code_interpreter or test_rag)" \
             --text-model="ollama/llama3.2:3b-instruct-fp16" \
             --embedding-model=all-MiniLM-L6-v2 \
-            --safety-shield=ollama \
+            --safety-shield=$SAFETY_MODEL \
             --color=yes \
             --capture=tee-sys | tee pytest-${{ matrix.test-type }}.log