Fix gcp-postgres teardown: skip re-download and re-start of proxy

The init function runs for both 'up' and 'down'. On teardown, curl
fails writing the binary (exit code 23) because the running proxy
holds it. Skip download if binary exists and skip proxy start if
already running.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: eakmanrq <6326532+eakmanrq@users.noreply.github.com>

Author: eakmanrq

.github/scripts/manage-test-db.sh

@@ -103,14 +103,16 @@ clickhouse-cloud_init() {
 
 # GCP Postgres
 gcp-postgres_init() {
-    # Download and start Cloud SQL Proxy
-    curl -fsSL -o cloud-sql-proxy https://storage.googleapis.com/cloud-sql-connectors/cloud-sql-proxy/v2.18.0/cloud-sql-proxy.linux.amd64
-    chmod +x cloud-sql-proxy
+    # Download Cloud SQL Proxy if not already present
+    if [ ! -f cloud-sql-proxy ]; then
+        curl -fsSL -o cloud-sql-proxy https://storage.googleapis.com/cloud-sql-connectors/cloud-sql-proxy/v2.18.0/cloud-sql-proxy.linux.amd64
+        chmod +x cloud-sql-proxy
+    fi
     echo "$GCP_POSTGRES_KEYFILE_JSON" > /tmp/keyfile.json
-    ./cloud-sql-proxy --credentials-file /tmp/keyfile.json $GCP_POSTGRES_INSTANCE_CONNECTION_STRING &
-
-    # Wait for proxy to start
-    sleep 5
+    if ! pgrep -x cloud-sql-proxy > /dev/null; then
+        ./cloud-sql-proxy --credentials-file /tmp/keyfile.json $GCP_POSTGRES_INSTANCE_CONNECTION_STRING &
+        sleep 5
+    fi
 }
 
 gcp-postgres_exec() {