[TTS] Tone/prosody matching - adjust speech emotion and style per line

[Ironship]

Problem

No way to adjust tone, emotion, or prosody per subtitle line. All lines are generated with the same flat settings.

Current behavior

• Edge-TTS has global rate/pitch/volume settings but not per-line
• ElevenLabs has stability/similarity/style sliders but only global
• Murf has voice styles but only one style per generation
• AllTalk has no tone/prosody API parameters

Proposed solution

• Add per-line prosody settings in ReviewSpeech window (rate, pitch, emotion)
• For ElevenLabs v3: leverage emotional context tags in text (ref: elevenlabs.io/blog/eleven-v3-audio-tags)
• For Edge-TTS: generate per-line SSML with prosody tags
• For Murf: allow style selection per line from AvailableStyles[]
• Store per-line settings in TtsStepResult or new model

Files affected

• src/UI/Features/Video/TextToSpeech/ReviewSpeech/ReviewSpeechViewModel.cs
• src/UI/Features/Video/TextToSpeech/ReviewSpeech/ReviewRow.cs - add prosody fields
• src/UI/Logic/Download/TtsDownloadService.cs - pass prosody params
• Engine files for SSML/parameter support

---

Working on this: @Ironship