fix: use draft()+thumbnail() to prevent OOM kill on large image resize

PIL img.resize() on high-resolution photos was exhausting worker RAM,
causing Gunicorn to SIGKILL the worker mid-request (production OOM crash).

Replace the explicit resize() path in both _compress_image_for_pdf() and
_compress_image_for_docx() with:
  - Image.draft() — hints the JPEG decoder to decode at a lower resolution
  - Image.thumbnail() — in-place resize that avoids allocating a second
    full-resolution buffer

This keeps peak memory proportional to the output size instead of the
original file size, preventing the worker from being killed when
processing multi-megapixel service-record photos.

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

backend/modules/fleet/views.py

@@ -468,15 +468,18 @@ 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.
+
+    Koristi Image.draft() + thumbnail() kako bi se izbjeglo učitavanje pune rezolucije
+    velikih fotografija u RAM (sprječava OOM kill Gunicorn workera).
     """
     try:
         image_field.open('rb')
         with Image.open(image_field) as src:
+            # draft() smanjuje dekodiranu rezoluciju za JPEG na serveru (hint, ne garantija)
+            src.draft('RGB', (max_width, max_width * 4))
             img = src.convert('RGB')
-            if img.width > max_width:
+            # thumbnail() radi in-place i ne alocira novu sliku pune veličine
-                ratio = max_width / float(img.width)
+            img.thumbnail((max_width, max_width * 4), Image.LANCZOS)
-                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)
@@ -493,15 +496,16 @@ def _compress_image_for_pdf(image_field, max_width=1280, quality=75):
 def _compress_image_for_docx(image_field, max_width=1600, quality=80):
     """
     Pripremi sliku za python-docx kao JPEG stream razumne veličine.
+
+    Koristi Image.draft() + thumbnail() kako bi se izbjeglo učitavanje pune rezolucije
+    velikih fotografija u RAM (sprječava OOM kill Gunicorn workera).
     """
     try:
         image_field.open('rb')
         with Image.open(image_field) as src:
+            src.draft('RGB', (max_width, max_width * 4))
             img = src.convert('RGB')
-            if img.width > max_width:
+            img.thumbnail((max_width, max_width * 4), Image.LANCZOS)
-                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)