Add classic eye image assets and import scripts

- Generate 18 classic eye variants in 3 styles (realistic, anime, cartoon)
  with 6 colors each (blue, green, brown, hazel, grey, amber)
- Add scripts for generating, converting, and importing eyes:
  - generate_classic_eyes_ppm.py: Generate PPM images (no dependencies)
  - download_classic_eyes.py: Full-featured generator with PIL
  - startup_import_eyes.py: Import eyes on backend startup
  - import_saved_eyes.py: Import from saved directory
- Update docker-compose to mount scripts directory
- Include metadata.json for tracking eye properties

data/classic_eyes_ppm/convert_to_png.py

@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+"""Convert PPM files to PNG using PIL."""
+from pathlib import Path
+from PIL import Image
+
+ppm_dir = Path(__file__).parent
+for ppm_file in ppm_dir.glob("*.ppm"):
+    png_file = ppm_file.with_suffix('.png')
+    img = Image.open(ppm_file)
+    img.save(png_file, 'PNG')
+    print(f"Converted: {ppm_file.name} -> {png_file.name}")