Configure template target cells and add skip-errors mode

src/taetigkeitsnachweis/validator.py

@@ -319,12 +319,13 @@ def validate_business_rules(
 
     if template_path.exists():
         template_wb = load_workbook(template_path, data_only=True)
-        if len(template_wb.sheetnames) != 1:
+        configured_sheet = config["sheets"].get("template_source", "")
+        if configured_sheet not in template_wb.sheetnames:
             issues.append(
                 ValidationIssue(
-                    code="TEMPLATE_SHEET_COUNT",
+                    code="TEMPLATE_SHEET_MISSING",
                     message=(
-                        f"Template workbook must contain exactly one sheet, found {len(template_wb.sheetnames)}."
+                        f"Configured template sheet '{configured_sheet}' not found in template workbook."
                     ),
                     severity="error",
                 )