v7: standalone Sing Detect app — full Tauri project tree

Promotes the v6 detection slice into a complete, buildable Tauri 2 app and
renames Stream Studio → Sing Detect (detection-only; video-concat split to its
own project). Proper src/ + src-tauri/ layout, Python sidecar under sidecar/,
app icons, package/Cargo manifests, and dev/build/pack scripts.

Pipeline unchanged in spirit: Rust drives ffmpeg to a 16 kHz mono WAV, the
Python sidecar (inaSpeechSegmenter) emits line-JSON segments, and Rust writes
EDL / markers CSV / CSV / JSON exports. Long ops run on spawn_blocking; cancel
kills the whole py -3.10 process tree.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

build.bat

@@ -0,0 +1,15 @@
+@echo off
+REM Sing Detect - build a distributable Windows app (MSI installer).
+REM Output: src-tauri\target\release\bundle\msi\
+setlocal
+set "PATH=%USERPROFILE%\.cargo\bin;%PATH%"
+
+if not exist "node_modules" call npm install
+
+echo Building release bundle (this takes a few minutes the first time)...
+call npm run tauri build
+
+echo.
+echo Done. Find the installer under:
+echo   src-tauri\target\release\bundle\msi\
+pause