perf(docker): improve pd/store/server image build cache efficiency

[bitflicker64]

Purpose of the PR

close #2977

Main Changes

.dockerignore (new file)

• Minimal, intentionally lean — only Docker-specific extras (.git, .github, compose files, docs)
• Most patterns already covered by .gitignore, not duplicated per maintainer guidance

All 4 Dockerfiles

• Added COPY --parents **/pom.xml ./ before COPY . . — pom layer only invalidates on pom changes, not source changes
• Added --mount=type=cache,target=/root/.m2 on mvn package — deps cached across repeated builds
• Removed vim, cron, service cron start, rm /var/lib/dpkg/info/libc-bin.*, dead code from runtime stage

Note: dependency:go-offline not used — inter-module deps like hg-pd-client aren't on Maven Central and would cause it to fail.

Verifying these changes

• Need tests and can be verified as follows:

docker build -f hugegraph-pd/Dockerfile -t hugegraph-pd:cache-test .
docker build -f hugegraph-store/Dockerfile -t hugegraph-store:cache-test .
docker build -f hugegraph-server/Dockerfile -t hugegraph-server:cache-test .
docker build -f hugegraph-server/Dockerfile-hstore -t hugegraph-server-hstore:cache-test .

Does this PR potentially affect the following parts?

• Dependencies (add/update license info & regenerate_known_dependencies.sh)
• Modify configurations
• The public API
• Other affects (typed here)
• Nope

Documentation Status

• Doc - No Need

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 1.56%. Comparing base (e108076) to head (4cc2e42).

❗ There is a different number of reports uploaded between BASE (e108076) and HEAD (4cc2e42). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (e108076)	HEAD (4cc2e42)
	3	2

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #3025       +/-   ##
============================================
- Coverage     35.85%   1.56%   -34.30%     
+ Complexity      338      43      -295     
============================================
  Files           802     780       -22     
  Lines         67995   65480     -2515     
  Branches       8902    8454      -448     
============================================
- Hits          24381    1026    -23355     
- Misses        41008   64368    +23360     
+ Partials       2606      86     -2520     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR aims to improve Docker build cache efficiency for HugeGraph PD, Store, and Server images by adding Docker context filtering and BuildKit/Maven cache-related Dockerfile changes.

Changes:

• Adds a new root .dockerignore.
• Updates four Dockerfiles to use a pom-only copy layer and Maven cache mounts.
• Removes some runtime packages and cleanup/startup commands from image build stages.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
.dockerignore	Adds Docker build-context exclusions.
hugegraph-pd/Dockerfile	Refactors PD image build layers and runtime dependency install.
hugegraph-store/Dockerfile	Refactors Store image build layers and runtime dependency install.
hugegraph-server/Dockerfile	Refactors Server image build layers and runtime dependency install.
hugegraph-server/Dockerfile-hstore	Refactors hstore Server image build layers and runtime dependency install.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.