feat: add edge tts backend and improve voice selection

[aegbirou]

Summary / 概述

Add an Edge TTS backend powered by edge-tts-rust and improve the TTS voice selection UX. This also sets the default Edge voice to zh-CN-XiaoyiNeural.

Changes / 变更内容

• Add a new Rust edge_tts backend using edge-tts-rust, including voice list loading, streaming synthesis, and default/fallback voice handling
• Improve the TTS settings UI with searchable voice selection for large voice lists and better select behavior
• Align current-provider voice editing with the existing TTS settings flow so the active voice is configured from Current Settings and persisted back on save
• Set the default Edge voice to zh-CN-XiaoyiNeural

Type / 类型

• feat — New feature / 新功能
• fix — Bug fix / Bug 修复
• refactor — Code refactoring / 代码重构
• docs — Documentation / 文档
• style — UI/CSS changes / 界面样式
• test — Tests / 测试
• chore — Build/tooling / 构建工具

Testing / 测试

• npm run tauri dev runs without errors
• npx tsc --noEmit passes
• cargo check passes
• Manually tested the feature

Screenshots / 截图

Related Issues / 相关 Issue

[chyinan]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

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