Add service and standalone script to import all cases from the master
Excel workbook into the database. Handles 5 year-sheets (2020-2022,
2023, 2024, 2025, 2026) with dynamic column mapping, fallgruppe
normalization, boolean/date parsing, phone number formatting, and
duplicate detection. Supports dry-run mode and per-sheet import.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
