Update MiniMax models to use the new M2.5 series. This PR includes the M2.5
model updates from MiniMax-M2.5.
- Update default model from MiniMax-M2.1 to MiniMax-M2.5
- Add new M2.5 models with reasoning support (M2.5, M2.5-Lightning)
- Keep M2.1-lightning for backwards compatibility
- Update UI labels to reflect M2.5 as recommended
- Add M2.5 to live model filter