docs: add endpoint contract (GitHub dispatch + Weblate)

[leostar0412]

Closes #9

Summary

Adds a first-pass integration contract for operators: HTTP surfaces between this repo and GitHub / Weblate, with pointers to authoritative code in cppalliance/weblate.

Changes

• New docs/endpoint-contract.md: endpoint inventory, GitHub repository_dispatch notes (add-submodules, start-translation, sync-translation), Weblate POST …/boost-endpoint/add-or-update/ caller vs server behavior, optional GET …/boost-endpoint/, WEBLATE_URL / URL_PREFIX guidance, risks, backlog, source index.
• README.md: Integration contracts subsection linking to the doc.

Summary by CodeRabbit

• Documentation
  • Added integration contract documentation detailing HTTP endpoints, request/response specifications, authentication methods, and payload requirements for GitHub dispatch and Weblate integrations.
  • Updated README to reference new integration documentation for improved visibility into integration surfaces.

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request adds documentation describing the HTTP integration contracts between this repository's GitHub dispatch workflows and the external Weblate Django app, including endpoint specifications, request/response schemas, authentication rules, and current gaps.

Changes

Integration Contract Documentation

Layer / File(s)	Summary
Documentation Overview README.md	"Integration contracts" section added, pointing readers to docs/endpoint-contract.md for detailed HTTP/GitHub/Weblate integration surfaces.
Contract Specification docs/endpoint-contract.md	New file documents GitHub repository_dispatch endpoints (start-translation, add-submodules, sync-translation), Weblate POST /boost-endpoint/add-or-update/ and GET /boost-endpoint/ contracts, including request/response schemas, authentication rules, timeout behavior, and error-handling gaps. Source indexes reference workflow/script locations and Weblate fork components.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

A rabbit hops through contracts so clear,
Integration surfaces, no secrets here!
GitHub to Weblate, the pathway is bright,
Documentation now shining so right! 🐰✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'docs: add endpoint contract (GitHub dispatch + Weblate)' is clear, specific, and directly describes the main change: documentation added for an integration contract. It accurately summarizes the primary objective of the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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