Add Speech AI plugin

[fasuizu-br]

Summary

Adds Speech AI plugin under a new AI & Speech category.

Speech AI is a Claude Code plugin providing:

• Pronunciation assessment with phoneme-level scoring (17MB model, <300ms latency)
• Text-to-speech synthesis
• Speech-to-text transcription
• 8 MCP tools for language learning, accessibility, and voice applications

This enables Claude Code users to add speech capabilities to their AI agents and applications.

Checklist

• New category added for AI & Speech tools (none existed)
• Entry follows the existing format
• Link points to a public GitHub repository with documentation