Modernize LeetCode sync robustness

[yurirocha15]

Summary

• add typed Pydantic models for config, LeetCode API payloads, and persisted question data
• move question DB storage into the solution repo under .leet2git/database.json with legacy pickle migration
• harden handler registration, generated Python formatting, CLI errors, and authenticated import pagination
• refresh README and CI labels for uv, Ruff, ty, and Python 3.11+

[yurirocha15]

@copilot Review this PR

[Copilot]

@copilot Review this PR

I reviewed the PR and found one blocking issue: LeetcodeClient no longer exposes get_latest_submission / async_get_latest_submission, which is a public API break on main (src/leet2git/leetcode_client.py). I’d request changes to restore compatibility (or add a deprecation shim) before approving.

[yurirocha15]

Addressed the compatibility issue.

get_latest_submission and async_get_latest_submission are restored. They now use the typed problem-list + submissions-history APIs instead of the Cloudflare-blocked /submissions/latest/ endpoint. Added tests for the success and missing-history paths.

Validation: make format, make lint, make utest, make build.

[yurirocha15]

@copilot review again.

[Copilot]

@copilot review again.

Re-reviewed. The previous blocking concern is fully addressed — get_latest_submission / async_get_latest_submission are restored (commit 6a8174e) with a clean implementation that paginates the submission history API instead of the Cloudflare-blocked /submissions/latest/ endpoint. Five new tests cover the happy path, pagination, and all error branches.

Broader review findings:

• No blocking issues.
• Pydantic typed models for config, API payloads, and question DB are well-structured.
• QuestionDB JSON-first storage with one-way pickle migration is correct.
• _request_json error handling covers HTTP errors, network errors, and non-JSON responses.
• import_all pagination with last_key / offset is consistent with the new SubmissionListResponse model.
• DefaultHandler and PythonHandler correctly accept AppConfig instead of Dict[str, Any].
• handler_registry.py is a clean replacement for the old subclass discovery.
• CI is green across all workflow runs.

Approved.