fix(mic): dictation 缺麦克风权限时不再抢前台焦点

[appergb]

摘要

Closes #166

把 dictation 路径里的 mic 权限请求改成直接调用系统权限 API，不再先 show_main_window / activateIgnoringOtherApps 抢到前台。

改动

• coordinator.rs::ensure_microphone_permission 不再走 request_microphone_from_foreground
• 设置页里用户手动点按钮触发权限提示的显式路径保持不变
• 缺权限时仍会走现有 capsule error 提示，不会静默吞掉

验证

• cargo check --manifest-path src-tauri/Cargo.toml ✅

@codex review

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

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