Add shared pre-push hook to run tests before pushing

Hook lives in .githooks/pre-push (tracked) and runs pytest inside the
Docker app container.  start.sh auto-configures core.hooksPath so new
clones pick it up on first run.

start.sh

@@ -60,6 +60,11 @@ start_docker() {
         build_flag="--build"
     fi
 
+    # Ensure git hooks are configured (idempotent)
+    if git rev-parse --git-dir &>/dev/null; then
+        git config core.hooksPath .githooks
+    fi
+
     echo "Starting all services with Docker Compose..."
     echo ""