feat: complete MiniMax LLM provider integration

Add full MiniMax provider support across the entire stack:

Backend:
- Add MINIMAX to LiteLLMProvider enum in db.py
- Add MINIMAX mapping to all provider_map dicts in llm_service.py,
  llm_router_service.py, and llm_config.py
- Add Alembic migration (rev 106) for PostgreSQL enum
- Add MiniMax M2.5 example in global_llm_config.example.yaml

Frontend:
- Add MiniMax to LLM_PROVIDERS enum with apiBase
- Add MiniMax-M2.5 and MiniMax-M2.5-highspeed to LLM_MODELS
- Add MINIMAX to Zod validation schema
- Add MiniMax SVG icon and wire up in provider-icons

Docs:
- Add MiniMax setup guide in chinese-llm-setup.md

MiniMax uses an OpenAI-compatible API (https://api.minimax.io/v1)
with models supporting up to 204K context window.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

surfsense_web/components/icons/providers/index.ts

@@ -12,6 +12,7 @@ export { default as FireworksAiIcon } from "./fireworksai.svg";
 export { default as GeminiIcon } from "./gemini.svg";
 export { default as GroqIcon } from "./groq.svg";
 export { default as HuggingFaceIcon } from "./huggingface.svg";
+export { default as MiniMaxIcon } from "./minimax.svg";
 export { default as MistralIcon } from "./mistral.svg";
 export { default as MoonshotIcon } from "./moonshot.svg";
 export { default as NscaleIcon } from "./nscale.svg";

surfsense_web/components/icons/providers/minimax.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path fill="currentColor" d="M21.6 4.8h-2.4l-4.2 7.2-3-5.16h-.01L9 12 4.8 4.8H2.4L9 16.14V20.4h2.4v-4.2h1.2v4.2h2.4v-4.26z"/></svg>