Standalone Shonar Desktop: vendor portable sources + local engine; decouple from ~/Projects/Shonar

- shared/ = portable Android-origin sources vendored from deferred/desktop-server
  (app/build.gradle.kts srcDir repointed; PlaybackController.kt excluded as Android-only)
- backend/ = bundled-lite engine (SQLite + inline queue); .venv symlinked from the
  old checkout, PYTHONPATH pins THIS backend's code over any editable install
- repoRoot() resolves this project dir (env SHONAR_REPO still wins); desktop-dev.sh
  watches shared/ + backend/
- Verified: :app:compileKotlin + :app:test green (23 tests); engine boots on :8010,
  self-migrates, /healthz ok

launch-desktop.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+# Launch the SHONAR desktop app (packaged binary, no Gradle needed).
+set -euo pipefail
+cd "$(dirname "$0")"
+BIN="app/build/compose/binaries/main/app/shonar-desktop/bin/shonar-desktop"
+if [ ! -x "$BIN" ]; then
+  echo "Desktop build not found. Run: ./gradlew :app:createDistributable" >&2
+  exit 1
+fi
+export DISPLAY="${DISPLAY:-:0}"
+exec "$BIN"