fix: Langfuse SDK v4 migration, tracing improvements, and LLM config

- Langfuse SDK v4: fix prompt-to-trace linking (as_type=generation)
- tracing: compile_prompt with Langfuse managed prompt fallback
- journey: remove journey CLI subcommand (keep only interactive)
- LLM: add service-specific llm modules for batch-agent and chat
- gitignore: exclude eval private test data
- config: add LANGFUSE settings to shared config

shared/llm.py

@@ -33,6 +33,8 @@ def _api_key_for_model(model: str) -> str | None:
         return settings.GOOGLE_API_KEY or None
     if model.startswith("cerebras/"):
         return settings.CEREBRAS_API_KEY or None
+    if model.startswith("github/"):
+        return settings.GITHUB_TOKEN or None
     if model.startswith("github_copilot/"):
         return None
     return settings.OPENAI_API_KEY or None
@@ -49,6 +51,9 @@ def get_llm(
     if settings.GITHUB_COPILOT_TOKEN_DIR:
         os.environ.setdefault("GITHUB_COPILOT_TOKEN_DIR", settings.GITHUB_COPILOT_TOKEN_DIR)
 
+    if settings.GITHUB_TOKEN:
+        os.environ.setdefault("GITHUB_TOKEN", settings.GITHUB_TOKEN)
+
     if "/" in model:
         return ChatLiteLLM(model=model, temperature=temperature, callbacks=callbacks)