- Adds OcrResponse Pydantic schema for OCR branch JSON output.
- Validates invoice_date and due_date as strict ISO 8601 calendar dates.
- Adds field descriptions to InvoiceLineItem for clearer VLM prompts.
- Expands schema tests for dates, decimal coercion, negatives, and line_items_sum().
Adds the uv lockfile generated from pyproject.toml and updates
tool.mypy.python_version to 3.12 so third-party stubs parse cleanly
while keeping runtime compatibility at Python 3.11.