fix: omoguci rucni unos vremena u mjesecnom izvjestaju

Dodaje uredski unos pocetka i kraja rada u sidebaru mjesecnog izvjestaja servisera i automatski racuna redovan rad iz unesenog raspona. Zadrzava postojece predpopunjavanje za rad u uredu i validira neispravan vremenski raspon.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/modules/fleet/models.py

@@ -748,25 +748,47 @@ class MonthlyServicerDayEntry(BaseModel):
     def __str__(self):
         return f"{self.user_id} @ {self.entry_date} ({self.entry_type})"
 
+    def _calculate_regular_hours(self, start_time, end_time):
+        if start_time is None or end_time is None:
+            return Decimal('8.00')
+
+        start_minutes = (start_time.hour * 60) + start_time.minute + (start_time.second / 60)
+        end_minutes = (end_time.hour * 60) + end_time.minute + (end_time.second / 60)
+        if end_minutes <= start_minutes:
+            raise ValidationError({
+                'end_time': _('Kraj rada mora biti nakon početka rada.'),
+            })
+
+        hours = Decimal(str((end_minutes - start_minutes) / 60)).quantize(Decimal('0.01'))
+        return hours
+
     def apply_defaults(self):
+        start_time = self.start_time
+        end_time = self.end_time
+
         if self.entry_type == 'office':
-            self.description = 'Rad u uredu'
-            self.location = 'Zagreb (ured)'
-            self.start_time = time(8, 0)
-            self.end_time = time(16, 0)
-            self.regular_hours = Decimal('8.00')
-            self.overtime_hours = Decimal('0.00')
-            return
-
-        if self.entry_type == 'vacation':
-            self.description = 'Godišnji odmor'
+            if not self.description:
+                self.description = 'Rad u uredu'
+            if not self.location:
+                self.location = 'Zagreb (ured)'
+            if start_time is None:
+                start_time = time(8, 0)
+            if end_time is None:
+                end_time = time(16, 0)
+        elif self.entry_type == 'vacation':
+            if not self.description:
+                self.description = 'Godišnji odmor'
+            self.location = self.location or ''
         elif self.entry_type == 'sick_leave':
-            self.description = 'Bolovanje'
+            if not self.description:
+                self.description = 'Bolovanje'
+            self.location = self.location or ''
+        else:
+            self.location = self.location or ''
 
-        self.location = ''
-        self.start_time = None
-        self.end_time = None
-        self.regular_hours = Decimal('8.00')
+        self.start_time = start_time
+        self.end_time = end_time
+        self.regular_hours = self._calculate_regular_hours(start_time, end_time)
         self.overtime_hours = Decimal('0.00')
 
     def clean(self):