fix(services): align bound service operations with OpenAPI REST contracts

[robbecker-wf]

Stacked PR: Part 3 of 7

Stack Overview:

1. #443 10x-openapi-spec-baseline -> 10x
2. #444 10x-security-and-transport -> 10x-openapi-spec-baseline
3. #445 10x-service-contracts-conformance (this PR) -> 10x-security-and-transport
4. #446 10x-schema-models-and-strict-analysis -> 10x-service-contracts-conformance
5. #447 10x-test-pyramid-and-smoke -> 10x-schema-models-and-strict-analysis
6. #448 10x-ci-and-spec-sync -> 10x-test-pyramid-and-smoke
7. #449 10x-conformance-plan -> 10x-ci-and-spec-sync

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Summary

Repairs bound service operations against the OpenAPI specification contract definitions.

• Activity: Fixed notification thread endpoint path (/notifications/threads/{id}) and updated star / unstar return types and status codes (204 No Content).
• Gists: Fixed HTTP methods (PATCH for edit, PUT for star) and set explicit status code 201 for comments.
• Git: Handled refs/ prefix correctly on createReference, editReference, and deleteReference; used query parameters for getTree recursive mode.
• Issues: Used PUT for issue locking, renamed assignee parameter, and corrected replaceLabelsForIssue return type to List<IssueLabel>.
• Organizations: Updated editTeam to use PATCH and added editTeamInOrg.
• Repositories: Added createDispatchEvent, listTopics, and replaceTopics; ensured status 201 for release assets.
• Search: Replaced custom rate-limit exceptions with standardized transport error decoding.
• Contract Tests: Added comprehensive conformance tests in test/contract/service_contracts_test.dart.