- Dockerfile: use Flutter tarball instead of git clone (~150MB vs 500MB+) - Dockerfile: split into independent layers for better caching - Dockerfile: use JRE instead of JDK, remove unnecessary packages - devcontainer.json: remove venv/pip/claude from postCreateCommand - ci.yml: remove redundant analyze/test in build-android job - ci.yml: run lint and test in parallel (no dependency chain) Estimated impact: 40min -> ~5-8min first build, ~2-3min cached