fix: address PR review issues for catalogue images

- Use PNG format instead of JPEG for transparency support
- Non-strict mode only resizes if image width > target width
- Replace CATALOGUE_BACKGROUND_IMAGES_COLOR with CATALOGUE_BACKGROUND_IMAGES_RGBA (tuple default (0,0,0,0))
- Move all inline imports to top of test file
- Add test_resize_non_strict_no_upscale test case
- Add comment explaining settings.DEBUG guard for media serving

tienda_ilusion/config/settings/base.py

@@ -146,7 +146,12 @@ MEDIA_URL = "/media/"
 CATALOGUE_IMAGE_WIDTH = int(os.environ.get("CATALOGUE_IMAGE_WIDTH", "600"))
 CATALOGUE_IMAGE_HEIGHT = int(os.environ.get("CATALOGUE_IMAGE_HEIGHT", "600"))
 CATALOGUE_STRICT_DIMENSION = os.environ.get("CATALOGUE_STRICT_DIMENSION", "False").lower() in ("true", "1", "yes")
-CATALOGUE_BACKGROUND_IMAGES_COLOR = os.environ.get("CATALOGUE_BACKGROUND_IMAGES_COLOR") or None
+CATALOGUE_BACKGROUND_IMAGES_RGBA = os.environ.get(
+    "CATALOGUE_BACKGROUND_IMAGES_RGBA", "0,0,0,0"
+)
+# Parse RGBA string to tuple
+_rgba_parts = CATALOGUE_BACKGROUND_IMAGES_RGBA.split(",")
+CATALOGUE_BACKGROUND_IMAGES_RGBA = tuple(int(p.strip()) for p in _rgba_parts)
 CATALOGUE_MAX_UPLOAD_SIZE = int(os.environ.get("CATALOGUE_MAX_UPLOAD_SIZE", str(5 * 1024 * 1024)))
 
 # Default primary key field type