refactor: add strict_mode publish gate & bump V2 version (#13)

Add concurrency group and a new resolve_source job that fetches the master commit SHA from apache/hugegraph and exposes it as SOURCE_SHA. Use SOURCE_SHA for actions/checkout in integration_precheck and publish_matrix (replacing the previous hardcoded branch), and make publish_matrix depend on resolve_source with an updated success condition. Replace hardcoded local image names in the compose override with PD/STORE/SERVER image variables and remove quoted heredoc to enable substitution. Add curl connection and max timeouts for readiness probes to avoid hanging.

Author: imbajin