feat: add MiniMax as cloud LLM provider

[octo-patch]

Summary

Adds MiniMax as an alternative cloud LLM provider alongside Ollama, enabling users to chat with MiniMax-M2.7, M2.7-highspeed, M2.5 and M2.5-highspeed models directly from the terminal.

Changes

• minimaxclient.py: New MiniMaxLLM client with SSE streaming via httpx, tool call support, <think> tag parsing for thinking mode, and temperature clamping to [0, 1.0]
• chat_edit.py: Provider selector (RadioSet: Ollama / MiniMax) in the model selection screen — MiniMax option is automatically disabled when MINIMAX_API_KEY is not set
• config.py: MINIMAX_API_KEY and MINIMAX_BASE_URL environment variables
• types.py: provider field on ChatModel (defaults to "ollama" for backward compatibility)
• store.py + v0_14_8.py: Database migration to persist provider per chat session
• chat.py: _create_llm_client() factory that routes to the correct client based on provider, plus httpx.HTTPStatusError error handling
• 31 unit tests + 3 integration tests covering model listing, think-tag parsing, temperature clamping, streaming, and live API calls

Configuration

export MINIMAX_API_KEY="your-key-here"
# Optional: export MINIMAX_BASE_URL="https://api.minimax.io/v1"
oterm

When MINIMAX_API_KEY is set, a provider toggle appears in the chat creation screen.

No breaking changes

• Existing Ollama-only workflows are unaffected (provider defaults to "ollama")
• No new Python dependencies (uses httpx already available via ollama)
• Database auto-migrates with ALTER TABLE chat ADD COLUMN provider

Test plan

• 31 unit tests pass (model types, think-tag parsing, temperature clamping, streaming with mocked HTTP)
• 3 integration tests pass against live MiniMax API
• Manual testing: create MiniMax chat, stream response, verify thinking mode, verify tool calls
• Verify existing Ollama tests still pass when Ollama server is available

[ggozad]

Hey!
I am contemplating switching everything to pydantic AI which would make oterm be able to use any provider.
Would it be ok wait a bit and see if I can pull it off soon, otherwise will look into this?

If you are willing to help let me know and I will open a PR next week if I make progress.