CLI: Fix onboard advisory about configuration files

[MichelSantos]

📝 Description

The onboarding advisory includes steps that are incorrect since v0.2.5. The PR updates the onboarding advisories to discuss the configuration file and the security file.

🗣️ Type of Change

• [☑️] 🐞 Bug fix (non-breaking change which fixes an issue)

🤖 AI Code Generation

• [☑️] 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

Technical Context

The onboarding advisory includes steps that are incorrect since v0.2.5. That version began expecting API keys in the .security.yml file. The existing onboard message is:

Next steps:
1. Add your API key to <configPath>

However, the API key should be added to <securityPath>, and the LLM name should be indicated in the model_name field of the <configPath>.

The PR updates the onboarding advisories to:

Next steps:
  1. Add your selected LLM to the `model_name` field in <configPath>
  2. Add your API key to <securityPath>

The advisory step numbers also adapt to:

• whether encryption is enabled, and
• "plain" or "fancy" UI is being used.

☑️ Checklist

• [☑️] My code/docs follow the style of this project.
• [☑️] I have performed a self-review of my own changes.
• I have updated the documentation accordingly.

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