fix: add editable work order travel expenses

Introduce a dedicated travel-expenses table for work orders so Broj sati, Količina dnevnica, and Iznos dnevnice can be reviewed and edited before PDF generation. The PDF now uses the stored travel-expenses values, with default HR rate and cache invalidation on updates.

backend/modules/fleet/models.py

@@ -417,6 +417,63 @@ class WorkOrderAdditionalCostsTable(BaseModel):
         return f"Additional costs table for work order {self.work_order_id}"
 
 
+class WorkOrderTravelExpensesTable(BaseModel):
+    RATE_CHOICES = [
+        ('HR', _("Hrvatska")),
+        ('BIH', _("BiH")),
+        ('SI', _("Slovenija")),
+        ('CG', _("Crna Gora")),
+    ]
+
+    DEFAULT_RATE_COUNTRY = 'HR'
+    DEFAULT_RATE_AMOUNT = Decimal('30.00')
+
+    work_order = models.OneToOneField(
+        WorkOrder,
+        on_delete=models.CASCADE,
+        related_name='travel_expenses_table',
+        verbose_name=_("Putni nalog"),
+    )
+    broj_sati = models.DecimalField(
+        max_digits=10,
+        decimal_places=2,
+        default=Decimal('0.00'),
+        verbose_name=_("Broj sati"),
+    )
+    kolicina_dnevnica = models.DecimalField(
+        max_digits=10,
+        decimal_places=2,
+        default=Decimal('0.00'),
+        verbose_name=_("Količina dnevnica"),
+    )
+    iznos_dnevnica = models.DecimalField(
+        max_digits=10,
+        decimal_places=2,
+        default=DEFAULT_RATE_AMOUNT,
+        verbose_name=_("Iznos dnevnice"),
+    )
+    daily_rate_country = models.CharField(
+        max_length=8,
+        choices=RATE_CHOICES,
+        default=DEFAULT_RATE_COUNTRY,
+        verbose_name=_("Država dnevnice"),
+    )
+    total_for_payout = models.DecimalField(
+        max_digits=12,
+        decimal_places=2,
+        default=Decimal('0.00'),
+        verbose_name=_("Ukupan iznos"),
+    )
+
+    class Meta:
+        ordering = ['-updated_at']
+        verbose_name = _("Tablica obračuna putnih troškova")
+        verbose_name_plural = _("Tablice obračuna putnih troškova")
+
+    def __str__(self):
+        return f"Travel expenses table for work order {self.work_order_id}"
+
+
 class WorkOrderPhoto(BaseModel):
     work_order = models.ForeignKey(
         WorkOrder,