Add built-in MiniMax provider presets

[octo-patch]

Reason: Add built-in MiniMax presets so users can select current models and the appropriate regional endpoint without custom configuration.

Changes

• Add global and China MiniMax provider presets.
• Configure the current MiniMax models and bearer-token environment variable.
• Add focused coverage for preset resolution and default model selection.

Checks

• bun test src/utils/model/providerConfig.test.ts
• bun run version
• git diff --check