feat: implement interactive arrow-key menus for provider and model selection

[Nithwin]

Is your feature request related to a problem? Please describe.

Currently, changing the AI provider or model via windmist set provider or windmist set model requires manual typing of exact string IDs (openai, claude-3-5-sonnet-latest, gpt-4o). This creates high user friction, typos, and requires users to memorize model names.

Describe the solution you'd like

1. Build/integrate a clean terminal selector (bubbletea menu) where users can use ↑ / ↓ arrow keys and press Enter to select from supported providers (gemini, openai, anthropic, groq, ollama).
2. When a provider is selected, automatically prompt the user with an interactive arrow-key menu of available models for that specific provider.
3. Specifically for Ollama, query the local Ollama daemon (http://localhost:11434/api/tags) over HTTP to dynamically populate the arrow-key menu with only the models currently downloaded and installed on the user's system.
4. Provide a "Custom model ID..." option at the bottom of the model list so users can still type a custom model if needed.

Describe alternatives you've considered

No response

Additional Context

No response