Intelligently initialize a decent default set of chat model options

Given the LLM landscape is rapidly changing, providing a good default
set of options should help reduce decision fatigue to get started

Improve initialization flow during first run
- Set Google, Anthropic Chat models too
  Previously only Offline, Openai chat models could be set during init

- Add multiple chat models for each LLM provider
  Interactively set a comma separated list of models for each provider

- Auto add default chat models for each provider in non-interactive
  model if the {OPENAI,GEMINI,ANTHROPIC}_API_KEY env var is set

- Do not ask for max_tokens, tokenizer for offline models during
  initialization. Use better defaults inferred in code instead

- Explicitly set default chat model to use
  If unset, it implicitly defaults to using the first chat model.
  Make it explicit to reduce this confusion

Resolves #882

docker-compose.yml

@@ -44,10 +44,19 @@ services:
       - KHOJ_DEBUG=False
       - KHOJ_ADMIN_EMAIL=username@example.com
       - KHOJ_ADMIN_PASSWORD=password
-      # Uncomment the following lines to make your instance publicly accessible.
-      # Replace the domain with your domain. Proceed with caution, especially if you are using anonymous mode.
+      # Uncomment lines below to use chat models by each provider.
+      # Ensure you set your provider specific API keys.
+      # ---
+      # - OPENAI_API_KEY=your_openai_api_key
+      # - GEMINI_API_KEY=your_gemini_api_key
+      # - ANTHROPIC_API_KEY=your_anthropic_api_key
+      # Uncomment the necessary lines below to make your instance publicly accessible.
+      # Replace the KHOJ_DOMAIN with either your domain or IP address (no http/https prefix).
+      # Proceed with caution, especially if you are using anonymous mode.
+      # ---
       # - KHOJ_NO_HTTPS=True
       # - KHOJ_DOMAIN=192.168.0.104
+      # - KHOJ_DOMAIN=khoj.example.com
     command: --host="0.0.0.0" --port=42110 -vv --anonymous-mode --non-interactive