feat: adding MiniMax LLM provider

[dandandandaann]

Pull Request Type

• ✨ feat (New feature)
• 🐛 fix (Bug fix)
• ♻️ refactor (Code refactoring without changing behavior)
• 💄 style (UI style changes)
• 🔨 chore (Build, CI, maintenance)
• 📝 docs (Documentation updates)

Relevant Issues

resolves #5298

Description

Add MiniMax (https://platform.minimax.io) as a new LLM provider.

• MiniMax-M2.7 — Peak Performance. Ultimate Value. Master the Complex.
• MiniMax-M2.7-highspeed — Same performance, faster and more agile.
  Updated docs.

Visuals (if applicable)

Additional Information

• Based on the Moonshot AI provider pattern (Moonshot AI LLM & agent provider #4178)
• MiniMax uses OpenAI-compatible API at https://api.minimax.io/v1
• MiniMax doesn't expose a /models endpoint, so static model list is used
• Added to README.md and localized README files

Developer Validations

• I ran yarn lint from the root of the repo & committed changes
• Relevant documentation has been updated (if applicable)
• I have tested my code functionality
• Docker build succeeds locally