Add MiniMax music generation tool

[octo-patch]

Reason: Add MiniMax music generation to the native media tool registry.

• Add a code-discovered music toolset with Music 3.0 and Music 2.6 paid and free generation models.
• Support global and China endpoints, regional watermarking, URL and hex output, streaming, and MP3/WAV/PCM audio settings.
• Validate conditional prompt and lyrics requirements and parse API status, audio, and error responses.

Checks:

• uv run ruff format --check intentkit/tools/music tests/tools/test_music.py
• uv run ruff check intentkit/tools/music tests/tools/test_music.py
• uv run basedpyright intentkit/tools/music tests/tools/test_music.py
• uv run --with 'psycopg[binary]' pytest -q tests/tools/test_music.py tests/tools/test_catalog_sync.py tests/tools/test_available_sync.py
• uv run lint-imports
• uv run --with 'psycopg[binary]' pytest -q tests/tools/test_tool_price_registry.py
• git diff --check