add: absorb soprano_to_rvc as regular subdirectory

Voice conversion pipeline (Soprano TTS → RVC) with Docker support.
Previously tracked as bare gitlink; removed .git/ directories and
absorbed into main repo for unified tracking.

Includes: Soprano TTS, RVC WebUI integration, Docker configs,
WebSocket API, and benchmark scripts.
Updated .gitignore to exclude large model weights (*.pth, *.pt, *.onnx, *.index).
287 files (3.1GB of ML weights properly excluded via gitignore).

soprano_to_rvc/.dockerignore

@@ -0,0 +1,66 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+*.egg-info/
+dist/
+build/
+
+# Virtual environments
+.venv/
+.venv-cuda/
+venv/
+ENV/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# Git
+.git/
+.gitignore
+
+# Documentation (not needed in containers)
+*.md
+!README.md
+
+# Archives
+archive_old_tests/
+backups/
+
+# Test files
+test_*.py
+benchmark_*.py
+diagnose_*.py
+monitor_*.sh
+*.txt.backup
+
+# Logs
+*.log
+
+# Docker files (don't copy into containers)
+Dockerfile*
+docker-compose*.yml
+.dockerignore
+
+# Build scripts (not needed in containers)
+*.sh
+!setup_alsa_bridge.sh
+
+# Config backups
+*.backup
+*.json.bak
+
+# Audio test files
+*.wav
+*.mp3
+*.flac
+
+# Large unnecessary files
+soprano/.git/
+Retrieval-based-Voice-Conversion-WebUI/.git/