Add an interactive setup script for efficiency

[cubrift]

To make onboarding as frictionless as possible for new users and self-hosters, we should replace/supplement manual .env file creation with an interactive, terminal-based setup CLI.

Some people are seriously lazy!

Running npm run setup should walk the user through key configurations with friendly prompts and automatically generate a valid .env file.

Proposed Approach

• Use @clack/prompts for clean terminal UI formatting.
• Prompt the user step-by-step for key variables:
• OpenAI API Key (OPENAI_API_KEY)
• GIPHY API Key (GIPHY_API_KEY)
• Preferred bot prefix / trigger settings
• Optional configuration options (e.g., custom database path or debug mode)
• Read from .env.example as a template to ensure all required fields are included.
• Safely write/overwrite the local .env file with validated inputs.

Tasks

• Add @clack/prompts CLI prompt dependency.
• Create scripts/setup.js (or .ts) to handle user input and validation.
• Add "setup": "node scripts/setup.js" to package.json scripts.
• Update README.md quickstart instructions to highlight npm run setup.

Acceptance Criteria

• Running npm run setup successfully generates a working .env file.
• Existing .env files are not overwritten without explicit user confirmation.
• Clear error messaging if a user provides an invalid format for required fields (like API key strings).