fix: ispravi prikaz računa u admin/frontendu i smanji PDF slike

- admin.py: thumbnail_preview u WorkOrderInvoiceInline i WorkOrderInvoiceAdmin
  prikazuje slike/PDF veze putem optimiziranog image endpointa
- serializers.py: image_url sada uključuje ?w=1280&q=80&fmt=jpeg za ne-PDF slike
- views.py: doda _compress_image_for_pdf() helper, zamijeni ImageReader(photo.image)
  s kompresiranom JPEG verzijom na oba mjesta u PDF generiranju
- tasks.py: kompresija invoice slike u JPEG u memoriji prije ImageReader poziva
- WorkOrderInvoicesPdfPage.jsx:
  * InvoiceImagePreview prikazuje 'Učitavanje...' dok se blob dohvaća (ne 401 fallback)
  * uklonjen resolveMediaUrl fallback koji uzrokuje 401 greške
  * svaka invoice kartica je klikabilna i otvara InvoiceDetailModal
  * InvoiceDetailModal prikazuje detalje i uvećanu sliku/PDF vezu

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

backend/modules/fleet/admin.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 from django.contrib import admin
 from django.contrib.admin import ModelAdmin
 from django.utils.html import format_html
@@ -61,8 +62,27 @@ class ServiceRecordInline(admin.TabularInline):
 class WorkOrderInvoiceInline(admin.TabularInline):
     model = WorkOrderInvoice
     extra = 0
-    fields = ('naziv_racuna', 'lokacija', 'datum', 'opis', 'image', 'created_by', 'created_at', 'is_active')
-    readonly_fields = ('created_at',)
+    fields = ('thumbnail_preview', 'naziv_racuna', 'lokacija', 'datum', 'opis', 'image', 'created_by', 'created_at', 'is_active')
+    readonly_fields = ('thumbnail_preview', 'created_at')
+
+    @admin.display(description="Pregled")
+    def thumbnail_preview(self, obj):
+        if not obj.pk or not obj.image:
+            return "—"
+        suffix = Path(obj.image.name or '').suffix.lower()
+        if suffix == '.pdf':
+            return format_html(
+                '<a href="/api/fleet/work-order-invoices/{}/image/" target="_blank">📄 PDF</a>',
+                obj.pk,
+            )
+        return format_html(
+            '<a href="/api/fleet/work-order-invoices/{}/image/?w=1600&q=90&fmt=jpeg" target="_blank">'
+            '<img src="/api/fleet/work-order-invoices/{}/image/?w=200&q=75&fmt=jpeg" '
+            'style="height:64px;width:auto;border-radius:4px;object-fit:cover;" />'
+            '</a>',
+            obj.pk,
+            obj.pk,
+        )
 
 
 class WorkOrderPhotoInline(admin.TabularInline):
@@ -193,10 +213,30 @@ class WorkOrderAdmin(admin.ModelAdmin):
 
 @admin.register(WorkOrderInvoice)
 class WorkOrderInvoiceAdmin(admin.ModelAdmin):
-    list_display = ('id', 'work_order', 'naziv_racuna', 'lokacija', 'datum', 'created_by', 'is_active')
+    list_display = ('id', 'image_preview', 'work_order', 'naziv_racuna', 'lokacija', 'datum', 'created_by', 'is_active')
     list_filter = ('datum', 'is_active', 'work_order')
     search_fields = ('naziv_racuna', 'lokacija', 'opis', 'work_order__id')
     ordering = ('-datum', '-created_at')
+    readonly_fields = ('image_preview', 'created_at')
+
+    @admin.display(description="Slika")
+    def image_preview(self, obj):
+        if not obj.pk or not obj.image:
+            return "—"
+        suffix = Path(obj.image.name or '').suffix.lower()
+        if suffix == '.pdf':
+            return format_html(
+                '<a href="/api/fleet/work-order-invoices/{}/image/" target="_blank">📄 PDF</a>',
+                obj.pk,
+            )
+        return format_html(
+            '<a href="/api/fleet/work-order-invoices/{}/image/?w=1600&q=90&fmt=jpeg" target="_blank">'
+            '<img src="/api/fleet/work-order-invoices/{}/image/?w=200&q=75&fmt=jpeg" '
+            'style="height:80px;width:auto;border-radius:4px;object-fit:cover;" />'
+            '</a>',
+            obj.pk,
+            obj.pk,
+        )
 
 
 @admin.register(WorkOrderAdditionalCostsTable)

backend/modules/fleet/serializers.py

@@ -373,9 +373,13 @@ class WorkOrderInvoiceSerializer(serializers.ModelSerializer):
             return None
         if request is None:
             return None
-        return request.build_absolute_uri(
+        base = request.build_absolute_uri(
             reverse('work-order-invoice-image', kwargs={'pk': obj.pk})
         )
+        suffix = Path(obj.image.name or '').suffix.lower()
+        if suffix == '.pdf':
+            return base
+        return f"{base}?w=1280&q=80&fmt=jpeg"
 
     def get_image_content_type(self, obj):
         if not obj.image:

backend/modules/fleet/tasks.py

@@ -645,10 +645,19 @@ def _build_work_order_invoices_pdf(work_order):
                     y = content_top
                     max_height = y - content_bottom
 
+                # Kompresiraj u JPEG u memoriji radi manje veličine PDF-a
+                compress_w = min(image.width, 1280)
+                if image.width > compress_w:
+                    ratio_c = compress_w / float(image.width)
+                    image = image.resize((compress_w, max(1, int(image.height * ratio_c))), Image.LANCZOS)
+                buf = BytesIO()
+                image.save(buf, format='JPEG', quality=75, optimize=True)
+                buf.seek(0)
+
                 ratio = min(max_width / float(image.width), max_height / float(image.height), 1.0)
                 draw_width = max(1, int(image.width * ratio))
                 draw_height = max(1, int(image.height * ratio))
-                image_reader = ImageReader(image)
+                image_reader = ImageReader(buf)
                 pdf.drawImage(
                     image_reader,
                     margin,

backend/modules/fleet/views.py

@@ -208,6 +208,32 @@ def _docx_filename(work_order, doc_type):
     return f"{display_code}.work-order.docx"
 
 
+def _compress_image_for_pdf(image_field, max_width=1280, quality=75):
+    """
+    Otvori image_field (Django FileField), kompresiraj na max_width JPEG u memoriji,
+    vrati ImageReader spreman za reportlab. Vraća None ako slika nije dostupna.
+    """
+    try:
+        image_field.open('rb')
+        with Image.open(image_field) as src:
+            img = src.convert('RGB')
+            if img.width > max_width:
+                ratio = max_width / float(img.width)
+                new_h = max(1, int(img.height * ratio))
+                img = img.resize((max_width, new_h), Image.LANCZOS)
+            buf = BytesIO()
+            img.save(buf, format='JPEG', quality=quality, optimize=True)
+            buf.seek(0)
+        return ImageReader(buf)
+    except Exception:
+        return None
+    finally:
+        try:
+            image_field.close()
+        except Exception:
+            pass
+
+
 def _get_cached_pdf(work_order, pdf_type):
     now = timezone.now()
     expected_filename = _pdf_filename(work_order, pdf_type)
@@ -1166,7 +1192,9 @@ def _build_work_order_service_records_pdf(work_order):
                     prepared = []
                     for photo in row_photos:
                         try:
-                            image_reader = ImageReader(photo.image)
+                            image_reader = _compress_image_for_pdf(photo.image)
+                            if image_reader is None:
+                                continue
                             source_w, source_h = image_reader.getSize()
                             if not source_w or not source_h:
                                 continue
@@ -1390,7 +1418,9 @@ def _build_service_record_pdf(service_record):
             prepared = []
             for photo in row_photos:
                 try:
-                    image_reader = ImageReader(photo.image)
+                    image_reader = _compress_image_for_pdf(photo.image)
+                    if image_reader is None:
+                        continue
                     source_w, source_h = image_reader.getSize()
                     if not source_w or not source_h:
                         continue