merge: 合并 upstream/main 并保留本地图片计费功能

backend/migrations/028_add_account_notes.sql

@@ -0,0 +1,7 @@
+-- 028_add_account_notes.sql
+-- Add optional admin notes for accounts.
+
+ALTER TABLE accounts
+ADD COLUMN IF NOT EXISTS notes TEXT;
+
+COMMENT ON COLUMN accounts.notes IS 'Admin-only notes for account';