feat: add remote pipeline API client and serialization

[Mbeaulne]

Description

API layer of the remote-pipeline stack. Base: master. Remote storage is not activated in this layer.

• Add the backend pipeline API client, account lookup, response/ownership validation, and stable-identity writes.
• Expose one-page summary listing with cursor, page size, and optional total count. Keep complete-catalog listing for callers that need every summary, without fetching pipeline definitions.
• Add lossless serialization for pipeline specs, arguments, and annotations, and extract annotation coercion from run submission without changing its behavior.

Review focus: the backend contract, pagination, and round-trip serialization independently of storage and UI wiring.

Related pull requests

#2746 → #2747 → #2748 → #2749 → #2750 → #2751 → #2739 → #2780 → #2783

How to test

The API and store tests passed together at #2748: 68 tests. This includes pagination defaults, explicit cursors, optional totals, malformed responses, and summary-only requests; it is not a new full-suite run at this layer.

pnpm exec vitest run src/services/cloudPipelineService.test.ts src/services/pipelineStorage/RemotePipelineStore.test.ts

At this layer, run pnpm exec vitest run src/services/cloudPipelineService.test.ts to check the API independently. Existing run-submission annotation behavior must remain unchanged. Integrated browser validation is tracked in #2739.

Change Size

Relative to master for this PR only. Changed lines = additions + deletions.

Category	Files	Added	Removed	Changed
Application code	3	+340	-32	372
Tests	1	+709	-0	709
Documentation / configuration	0	+0	-0	0
Total	4	+1049	-32	1081

Application code excludes test files. Tests include unit, component, and browser test source; test-runner configuration, CI, package scripts, compiler configuration, and documentation are counted separately.

[github-actions]

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