68d83807ad
- #54: Extract isAdmin() to src/middleware/auth.js, remove duplicates from 7 admin handlers - #55: Add WalletUtils.convertToUsd(), replace 8 switch-case blocks across 4 files - #56: Unify getBaseWalletType() — keep only WalletUtils version (most complete), remove duplicates from Wallet.js and userWalletsHandler.js New file: src/middleware/auth.js Net: -215 lines, +80 lines Closes: #54, #55, #56