Regenerate Python SDK for expense base currency

[sanka-change-bot]

Summary

Regenerate the Python sanka-sdk from the canonical public OpenAPI contract. Expense create and update now accept base_currency directly. This truthful spec refresh also includes already-shipped public API additions and overlaps the open Ferry SDK PR #9; it does not modify or close that PR.

Audit

• Requester: @haegwan
• Authoring identity: Sanka Change Bot
• Head SHA: 956d92d4212bbd332825943374dc7d00f83f66b6
• Risk: medium
• Deploy mode: none
• Production surface: PyPI sanka-sdk package (separate release required)

Validation

• /opt/homebrew/bin/uv run ruff check src/sanka_sdk && /opt/homebrew/bin/uv run python -m compileall -q src/sanka_sdk -> passed
• Fern generation and Ruff checks passed -> reported passed
• Verified base_currency 235098 round-trips as 235098.0 -> reported passed
• No-local-check reason: N/A
• Required GitHub checks must complete before landing.
• Valid review findings must be addressed before landing.

Change Safety

• Data or migration impact: Generated client code only. No database or production runtime changes.
• Rollback: Revert this generated SDK commit; no runtime deployment is involved.
• Monitoring: Review PublicExpenseMutationRequest and expense client signatures before any PyPI release.

Approval And Deployment Authorization

• The PR is ready for final human review; no intended code changes remain.
• The listed head SHA is the exact revision being presented for approval.

By approving this PR, the reviewer authorizes merge of the exact approved revision. This repository has no production deployment in this flow. A later push requires a new approval.