fix: create skins directory on startup

internal/config/config.go

@@ -4,6 +4,7 @@ package config
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"strconv"
 )
 
@@ -51,6 +52,14 @@ func Load() (*Config, error) {
 		return nil, fmt.Errorf("JWT_SECRET is required")
 	}
 
+	// Create storage directories if they don't exist.
+	if err := os.MkdirAll(cfg.CASDir, 0o755); err != nil {
+		return nil, fmt.Errorf("failed to create CAS directory: %w", err)
+	}
+	if err := os.MkdirAll(filepath.Join(cfg.SkinsDir, "aa"), 0o755); err != nil { // Create with subdirectory structure
+		return nil, fmt.Errorf("failed to create skins directory: %w", err)
+	}
+
 	return cfg, nil
 }