chore: baseline snapshot before moderation-strictness feature

Repo .git was damaged (refs/ missing, index truncated, object store near-empty).
Repaired via git init (rebuilt refs), stale index preserved as .git/index.corrupt-20260910.bak,
then full worktree committed as a rollback baseline.

internal/storage/picture.go

@@ -0,0 +1,13 @@
+// Copyright 2022 E99p1ant. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package storage
+
+const PictureKeyPrefix = "picture/"
+
+// MaxAvatarSize is the max avatar size which is 2MB.
+const MaxAvatarSize = 2 * 1024 * 1024
+
+// MaxBackgroundSize is the max background size which is 2MB.
+const MaxBackgroundSize = 2 * 1024 * 1024