fix: improve upscaling for pixel art icons

- Use integer scaling (2x, 3x, 4x) instead of fractional for sharp pixels
- Use NEAREST neighbor resampling (better for pixel art than Lanczos)
- Add sharpening filter after upscale
- Reduced padding to 85% so icons fill more of canvas

This produces much sharper results for game icons!

modules/tga_converter.py

@@ -420,7 +420,7 @@ class TGAConverter:
         Returns:
             New image with canvas size, source image centered
         """
-        from PIL import Image
+        from PIL import Image, ImageFilter
         
         canvas_w, canvas_h = canvas_size
         img_w, img_h = image.size
@@ -430,14 +430,23 @@ class TGAConverter:
         
         # Calculate scaling
         if upscale:
-            # Scale up to fit within canvas with some padding (e.g., 90%)
-            max_size = int(min(canvas_w, canvas_h) * 0.9)
+            # Scale up to fit within canvas with some padding (e.g., 85%)
+            max_size = int(min(canvas_w, canvas_h) * 0.85)
             scale = min(max_size / img_w, max_size / img_h)
             
             if scale > 1:  # Only upscale, never downscale
-                new_w = int(img_w * scale)
-                new_h = int(img_h * scale)
-                image = image.resize((new_w, new_h), Image.Resampling.LANCZOS)
+                # For pixel art/game icons, use integer scaling + NEAREST for sharpness
+                # Round scale to nearest integer for clean pixel edges
+                int_scale = max(1, round(scale))
+                new_w = img_w * int_scale
+                new_h = img_h * int_scale
+                
+                # Use NEAREST neighbor for pixel art - keeps edges sharp
+                image = image.resize((new_w, new_h), Image.Resampling.NEAREST)
+                
+                # Apply slight sharpening to reduce blur from the upscale
+                image = image.filter(ImageFilter.SHARPEN)
+                
                 img_w, img_h = new_w, new_h
         
         # Calculate centered position