feat: add MiniMax model support with M2.7 as default

[octo-patch]

Summary

• Add MiniMax-M2.7 and MiniMax-M2.7-highspeed as new model options (M2.7 first in list)
• Include MiniMax-M2.5 and MiniMax-M2.5-highspeed as alternative models
• Add MiniMax provider routing with api.minimax.io/v1 base URL
• Add MiniMax BYOK API key template for user-provided keys
• Register MiniMax in platform-enabled BYOK providers list

Why

MiniMax-M2.7 is the latest flagship model with enhanced reasoning and coding capabilities. Adding it as a first-class provider gives users another high-quality model option alongside existing providers.

Changes

File	Change
worker/agents/inferutils/config.types.ts	Add 4 MiniMax model entries (M2.7, M2.7-highspeed, M2.5, M2.5-highspeed)
worker/agents/inferutils/core.ts	Add minimax provider case with API base URL
worker/api/controllers/modelConfig/byokHelper.ts	Add minimax to BYOK provider list
worker/types/secretsTemplates.ts	Add MiniMax BYOK API key template

Testing

• Model entries follow existing patterns (ModelSize, creditCost, directOverride)
• Provider routing matches established switch-case pattern
• BYOK template follows existing template structure