fix(settings): valida csv_delimiter/decimal_separator/auto_logout_minutes (#23)

PUT /api/settings/ non validava nulla: un csv_delimiter vuoto o di piu'
caratteri arrivava intatto nel DB e faceva fallire csv.writer con TypeError
dentro close_run (500, run mai chiuso). Aggiunta validazione per chiave nota
(csv_delimiter 1 carattere fra , ; TAB |, csv_decimal_separator ',' o '.',
auto_logout_minutes vuoto o intero 1-480, company_name/company_logo_path
non vuoti) -> 422 sui valori fuori dominio. Chiavi non note passano senza
validazione (store generico).

Difesa in profondita' in production_export_service._csv_format: un
csv_delimiter gia' sporco nel DB (scritto prima di questa validazione) non
fa piu' fallire close_run, usa ';' e logga un WARNING.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/backend/services/production_export_service.py

@@ -11,6 +11,7 @@ files that open correctly in their Excel.
 """
 import csv
 import io
+import logging
 from datetime import datetime
 from pathlib import Path
 
@@ -25,10 +26,18 @@ from src.backend.models.orm.setting import SystemSetting
 from src.backend.models.orm.station import Station
 from src.backend.models.orm.task import RecipeSubtask
 
+logger = logging.getLogger(__name__)
+
 # Written under the upload directory: it is the volume that is already mounted and
 # backed up, so the files survive a container being replaced.
 EXPORT_SUBDIR = "statistics"
 
+# `csv.writer` requires a 1-character delimiter. PUT /api/settings/ validates this
+# going forward (gitea#23), but a value written before that guard existed must not
+# be able to make close_run fail: fall back and log instead of raising.
+_VALID_CSV_DELIMITERS = {",", ";", "\t", "|"}
+_FALLBACK_CSV_DELIMITER = ";"
+
 HEADER = [
     "production_run_id",
     "station_code",
@@ -75,8 +84,17 @@ async def _csv_format(db: AsyncSession) -> tuple[str, str]:
         )
     )
     decimal = decimal_row.scalar_one_or_none()
+
+    delimiter_value = delimiter.setting_value if delimiter else ","
+    if delimiter_value not in _VALID_CSV_DELIMITERS:
+        logger.warning(
+            "csv_delimiter non valido nel DB (%r): uso %r",
+            delimiter_value, _FALLBACK_CSV_DELIMITER,
+        )
+        delimiter_value = _FALLBACK_CSV_DELIMITER
+
     return (
-        delimiter.setting_value if delimiter else ",",
+        delimiter_value,
         decimal.setting_value if decimal else ".",
     )