Adds a "봇 목소리(TTS) 조절" panel to the voice-server dashboard so the four
controls can be tuned from the browser instead of only via env vars:
- 4 sliders (glyph speed, word gap, sentence gap, pitch) with live labels
- 미리듣기: synthesises a sample with the slider values WITHOUT changing the
live bot voice (new per-call overrides on MeloTTS.synth)
- 봇에 적용: commits the slider values to the live TTS instance; next reply uses
them. 기본값 button resets to the manual defaults.
Backend: GET/POST /api/tts/settings (clamped to the manual ranges) and POST
/api/tts/preview (returns audio/wav). Panel shows only when tts is a real
(non-mock) backend.
Verified end-to-end against a live dashboard instance: page renders the panel,
GET returns defaults, POST applies+clamps (pitch 99->12), preview returns a
valid wav and leaves the live settings unchanged; 29 tests pass.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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