[UI] Adjust week start date (#11934)

* Adjust week start date

Co-authored-by: Copilot <copilot@github.com>

* Change to global setting

---------

Co-authored-by: Copilot <copilot@github.com>

src/backend/InvenTree/common/setting/system.py

@@ -1210,6 +1210,20 @@ SYSTEM_SETTINGS: dict[str, InvenTreeSettingsKeyType] = {
         'default': True,
         'validator': bool,
     },
+    'WEEK_STARTS_ON': {
+        'name': _('Week Starts On'),
+        'description': _('Starting day of the week, for display in calendar views'),
+        'default': '1',
+        'choices': [
+            ('0', _('Sunday')),
+            ('1', _('Monday')),
+            ('2', _('Tuesday')),
+            ('3', _('Wednesday')),
+            ('4', _('Thursday')),
+            ('5', _('Friday')),
+            ('6', _('Saturday')),
+        ],
+    },
     'TEST_STATION_DATA': {
         'name': _('Enable Test Station Data'),
         'description': _('Enable test station data collection for test results'),