Extract CSS styles to separate files for better maintainability

- Create templates/brutalism.css, glassmorphism.css, neumorphism.css
- Update styles.py to read CSS from files instead of inline strings
- Support --template with .css files (auto-detects modern style)
- CSS files can now be edited with proper syntax highlighting

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

generate_report.py

@@ -230,9 +230,23 @@ def main():
         print(f"Error: Assets directory not found: {args.assets}")
         return 1
 
-    # Validate template only if not using modern style
-    if args.style and args.style in MODERN_STYLES:
+    # Determine style from --style or --template
+    style = args.style
+
+    # If no --style provided, check if --template points to a modern CSS file
+    if not style and args.template.endswith('.css'):
+        template_path = Path(args.template)
+        style_name = template_path.stem  # e.g., "brutalism" from "brutalism.css"
+        if style_name in MODERN_STYLES:
+            style = style_name
+
+    # Validate template/style
+    if style and style in MODERN_STYLES:
         template_path = SCRIPT_DIR / "templates" / "modern.html"
+        css_path = SCRIPT_DIR / "templates" / f"{style}.css"
+        if not css_path.exists():
+            print(f"Error: CSS file not found: {css_path}")
+            return 1
     else:
         template_path = SCRIPT_DIR / args.template
 
@@ -240,7 +254,7 @@ def main():
         print(f"Error: Template file not found: {template_path}")
         return 1
 
-    generate_report(args.db, args.output, args.top, args.assets, args.template, args.background, args.style)
+    generate_report(args.db, args.output, args.top, args.assets, args.template, args.background, style)
     return 0