switched from s3 to disk for saving icons

pipeline/03_icon_download/storage.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+var iconsDir string
+
+func initStorage(dir string) error {
+	iconsDir = dir
+	return os.MkdirAll(dir, 0755)
+}
+
+// hashToPath converts a SHA-256 hex hash to a sharded file path.
+// e.g., "abcdef1234..." → "icons/ab/cd/ef/abcdef1234..."
+func hashToPath(hash string) string {
+	if len(hash) < 6 {
+		return filepath.Join(iconsDir, hash)
+	}
+	return filepath.Join(iconsDir, hash[:2], hash[2:4], hash[4:6], hash)
+}
+
+// iconExists checks if an icon is already stored on disk (for dedup).
+func iconExists(hash string) bool {
+	_, err := os.Stat(hashToPath(hash))
+	return err == nil
+}
+
+// iconWrite saves icon data to disk in the sharded directory structure.
+func iconWrite(hash string, data []byte) error {
+	path := hashToPath(hash)
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return fmt.Errorf("mkdir: %w", err)
+	}
+	return os.WriteFile(path, data, 0644)
+}