feat(client): implement docling-serve-grpc service

[krickert]

This pull request introduces a professional gRPC client and service bridge for Docling Serve, designed for enterprise-grade pipeline integrations and long-term archival storage.

Key Enhancements

• Professional gRPC API Design: Implements the ai.docling.serve.v1 contract with strict versioning throughout both Protobuf and Java packages.
• Unique Request/Response Wrappers: Adheres to Google API Design and Buf linting standards by using dedicated wrapper messages for every RPC, ensuring future-proof method independence.
• Robust Null-Safety: Implements exhaustive defensive mapping for the entire Docling document schema, guarding all collections, boxed primitives, and enums.
• Server-Side Polling (Watch Pattern): Introduces "Watch" RPCs that manage asynchronous task monitoring on the server side, streaming status updates back to the client.
• Comprehensive Verification: Includes unit, bidirectional mapping, and Testcontainers-based integration suites (all 78 tests passing).
• JPMS Support: Fully compatible with the Java Platform Module System.

Closes #325

[edeandrea]

Thank you @krickert for this! You've definitely put a lot of thought & time into this.

If you don't mind, let me take a few days to go through all of this. I've just returned to the office this morning after being out all week, and I want to give this the thought and review it deserves.

[github-actions]

:java_duke: JaCoCo coverage report

Overall Project	20.63%	🔴

There is no coverage information present for the Files changed

[github-actions]

	Tests	Passed ✅	Skipped	Failed
Gradle Test Results (all modules & JDKs)	1170 ran	1170 passed	0 skipped	0 failed

Test	Result
No test annotations available

• View Gradle Test Results (all modules & JDKs)

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[edeandrea]

@all-contributors add @krickert for code,idea

[allcontributors]

@edeandrea

I've put up a pull request to add @krickert! 🎉

[edeandrea]

@all-contributors add @krickert for documentation, tests

[allcontributors]

@edeandrea

I've put up a pull request to add @krickert! 🎉

[edeandrea]

Hi @krickert - when you created the pull request it does not look like you checked the box "Allow edits from maintainers".

Is that something you can turn on? I'd like to add a few things so that the CI will pick up these new modules and run the tests/code coverage on the PR.

[krickert]

Oh no problem!! Done.

[edeandrea]

For some reason its still not letting me push on top of your commit. I think its because you created the PR from your main branch rather than a feature branch.

Anyways, can you make the following edits so that CI will run on the PR?

.github/workflows/build.yml

test-report-aggregation/build.gradle.kts

[krickert]

Yes. I'll do it within the hour

For some reason its still not letting me push on top of your commit. I think its because you created the PR from your main branch rather than a feature branch.

Anyways, can you make the following edits so that CI will run on the PR?

.github/workflows/build.yml

test-report-aggregation/build.gradle.kts

[krickert]

OK I was able to do it I think?

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