feat: refresh MiniMax model registry

[octo-patch]

Description

Refresh the MiniMax provider registry with the current M3 and M2.7 model details.

• Add MiniMax-M2.7 and update MiniMax-M3 context, modality, thinking, and output metadata.
• Preserve input-length and service-tier pricing in the catalog and cost calculation.
• Make the Anthropic-compatible Base URL configurable and document global and China endpoint options for both supported protocols.
• Add focused catalog, adapter, pricing, and SDK request-path tests.

Type of Change

• Bugfix
• New Feature
• Improvement
• Documentation Update

Checklist

• I have read the contributing guidelines.
• I have added tests to cover my changes.
• All applicable local checks passed.

Test Plan

• sh lint.sh ci
• REDIS_HOST=localhost uv run pytest -q tests/models/test_minimax_provider.py tests/models/test_llm_cost.py tests/core/test_cached_input_pricing.py tests/core/test_llm.py tests/models/test_llm_picker.py tests/config/test_config.py
• Non-database unit suite: 1,226 passed and 1 skipped.
• Provider routing tests with a test key: 4 passed.
• Database-backed tests require initdb and were not run locally.