fix: replace StealthEX with ChangeNOW for wallet deposits

- URL: https://changenow.io/exchange?from=eur&to={crypto}&fiatMode=true
- Removed amount selection from URL (ChangeNOW has it in UI)
- Renamed STEALTHEX_REF to CHANGENOW_REF in config
- Updated all UI labels from StealthEX to ChangeNOW

.env.example

@@ -29,9 +29,9 @@ COMMISSION_WALLET_USDT=
 COMMISSION_WALLET_USDC=
 COMMISSION_WALLET_ETH=
 
-# --- StealthEX Deposit Integration ---
-# Optional: your StealthEX referral ID (leave empty if none)
-STEALTHEX_REF=
+# --- ChangeNOW Deposit Integration ---
+# Optional: your ChangeNOW referral ID (leave empty if none)
+CHANGENOW_REF=
 
 # --- WireGuard ---
 WG_ENABLED=false