Add overseas stock endpoint coverage

[Bogyie]

Summary

• Add an inventory-backed overseas stock SDK surface for 51 listed endpoints across trading/account, quotation, market-analysis, and realtime-quotation collections.
• Expose collection slices and an execute_overseas_stock helper so callers can use stable SDK handles instead of raw operation ids.
• Extend SDK tests and docs to cover endpoint counts, mock-supported execution, required-query validation, ambiguous overseas order TR IDs, and live-trading blocking.
• Merge the latest bog-220-kis-sdk integration branch and preserve all already-merged sibling coverage: OAuth revoke/approval, overseas futures/options, realtime stock, listed bond, domestic stock REST, and domestic futures/options.

Verification

• git diff --check passed locally before the original commit.
• QA reported cargo fmt --check passed.
• QA reported cargo test --locked passed: mock contract 4 passed, sdk_core 20 passed, doctest 0 passed.
• QA reported cargo clippy --all-targets -- -D warnings passed.
• After resolving the PR Add overseas futures/options endpoint coverage #11 parent-branch conflict, cargo fmt --check, cargo test --locked (mock contract 4, sdk_core 25, doctest 0), and cargo clippy --all-targets -- -D warnings passed locally.
• After resolving the PR Add realtime stock and bond inventory helpers #14 parent-branch conflict, cargo fmt --check, cargo test --locked (mock contract 4, sdk_core 29, doctest 0), and cargo clippy --all-targets -- -D warnings passed locally.
• After resolving the PR Add OAuth revoke and approval APIs #10/Cover domestic stock REST inventory endpoints #12 parent-branch conflict, cargo fmt --check, cargo test --locked (mock contract 4, sdk_core 36, doctest 0), and cargo clippy --all-targets -- -D warnings passed locally.
• After resolving the PR Add domestic futures/options API coverage #13 parent-branch conflict, cargo fmt --check, cargo test --locked (mock contract 4, sdk_core 42, doctest 0), and cargo clippy --all-targets -- -D warnings passed locally.

QA Evidence

• Overseas stock catalog count: 51 endpoints.
• Collection counts: trading/account 18, quotation 14, market analysis 15, realtime quotation 4.
• SDK coverage test compares the enum/slice surface against the bundled inventory filtered set.
• Mock-supported overseas quotation read path executed successfully through the local mock contract.
• Missing required query fields fail local validation before network I/O.
• Overseas stock order TR ID ambiguity requires caller-supplied override.
• Real-environment overseas stock orders return KisError::LiveTradingDisabled before network I/O.

Reviews

• QA PASS was reported in BOG-252.
• Design review PASS was reported in BOG-252.
• Documentation review PASS was reported in BOG-252.
• Security review PASS was reported in BOG-252.

Notes

• No live KIS credentials, account, live API calls, or real order execution were used.
• Overseas order TR IDs vary by country, exchange, and order side, so the SDK does not choose among ambiguous inventory TR IDs automatically.
• No repository PR template or CONTRIBUTING file was present; checked README.md, Cargo.toml, and .github/workflows/publish-crates.yml for contribution-relevant rules.

Closes BOG-252.

[amazon-q-developer]

This PR successfully adds overseas stock endpoint coverage to the SDK. The implementation is well-structured with 51 endpoints organized across 4 collections (trading/account, quotation, market-analysis, and realtime-quotation), following the existing domestic stock patterns.

The changes include proper safety mechanisms (live trading blocks, TR ID ambiguity handling, validation before network I/O), comprehensive test coverage with 7 new test cases, and clear documentation updates in both README and usage guide. All tests pass as reported in the PR description.

The code is ready to merge.

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