build: hand containerised build artifacts back to the host user

The compose services bind-mount the repo and build as root, so every artifact
they leave in src-tauri/target belongs to root on the host. It accumulates:
11,124 such files had built up, enough that cargo clean and scripts/clean.sh
failed with EACCES — and a plain cargo build died part-way through, because
build scripts compile for the host and land in target/debug even when
cross-compiling to Android. That is what blocked the device build in this batch.

Restores ownership at the end of each containerised build, reading the intended
owner from the checkout so no uid has to be plumbed through from the host. A
no-op when not running as root, so the native build scripts call it
unconditionally.

Running the containers as the host uid is the tidier fix and stays open — it
needs the cargo/bun cache volumes moved off /root first, which is why this is
not a one-line user: directive.

TRACES: | DR-213

scripts/build-android.sh

@@ -115,3 +115,7 @@ fi
 echo ""
 echo "✅ APK build complete!"
 echo "📱 APK location: src-tauri/gen/android/app/build/outputs/apk/"
+
+# Containerised builds run as root against a bind-mounted tree; hand the
+# artifacts back to the host user. No-op when not root. See DR-213.
+"$(dirname "$0")/restore-ownership.sh"