feat(cli): add interactive init env bootstrap

[trinhchien]

Summary

• update vibe-trading init to guide users through interactive .env setup
• write config to agent/.env instead of ~/.vibe-trading/.env
• support provider selection for OpenRouter, OpenAI, Anthropic, DeepSeek, and Ollama
• add basic API-key validation and overwrite confirmation
• add regression tests for env rendering and init flow

Testing

• python3 -m py_compile agent/cli.py agent/tests/test_cli_init.py agent/tests/test_llm.py agent/tests/conftest.py
• import smoke test for cli.cmd_init

Closes #14

[warren618]

Thanks for picking this up @trinhchien — the interactive flow, key validation, and tests all look solid!

A couple of things to address before merging:

1. Provider list should match .env.example

The current PR has 5 providers (OpenRouter, OpenAI, Anthropic, DeepSeek, Ollama), but the project actually supports 11 providers — see agent/.env.example for the full list.

Specifically:

• Remove Anthropic — our backend uses OpenAI-compatible endpoints via LangChain; Anthropic's API is not compatible, so it would not work even if configured
• Add the missing providers: Gemini, Groq, DashScope/Qwen, Zhipu, Moonshot/Kimi, MiniMax, MIMO

Please use agent/.env.example as the source of truth for provider names, env var names, base URLs, and default models.

2. Unused _INIT_ENV_DIR variable

_INIT_ENV_DIR = Path.home() / ".vibe-trading" on line 1407 is no longer used since the path was changed to agent/.env. Please remove it.

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Everything else (Rich prompts, _render_env_content, tests) looks great. Just need the provider list aligned and the dead variable cleaned up. Thanks!

[trinhchien]

Addressed the review feedback in the latest push:

• aligned provider choices with
• removed Anthropic
• added the missing providers (Gemini, Groq, DashScope/Qwen, Zhipu, Moonshot/Kimi, MiniMax, MIMO)
• removed the unused legacy init-dir variable
• updated tests accordingly\n\nAlso re-ran quick smoke checks with and import validation.

[warren618]

LGTM — provider list now matches .env.example, unused variable removed, tests updated. Nice work!