MiniMax M3 is live: long context + native multimodality at 1/20th the price

Added support for MiniMax M3, a new frontier model featuring long context (up to 500K tokens at launch, with 1M planned) and native multimodality. Highlighted the underlying MiniMax Sparse Attention (MSA) architecture and its performance benefits (e.g., 15x faster decoding at long context). Detailed M3's capabilities in coding and agentic tasks, and updated pricing information to include M3 alongside M2.7, with specific considerations for long-context pricing tiers.