fix(web): correct asset IDs/decimals + chain routing, string-BigInt amounts, presale signer

Fund-logic hardening (audit remediation):
- TransferModal: source asset id/decimals from the canonical MINTABLE_ASSETS
  (wUSDT=1000, wDOT=1001, wETH=1002, wBTC=1003) instead of the wrong hardcoded
  ids (BTC=3 was the deprecated "Old USDT", ETH=4, DOT=5). Route every non-native
  asset through the Asset Hub api; only native HEZ uses the relay balances pallet.
  Removes the latent wrong-asset / wrong-chain transfer.
- Replace BigInt(parseFloat(x)*10**dec) with string-based parseTokenInput in
  TransferModal + 3 DEX init modals; BigInt(float) threw RangeError on common
  fractional amounts (e.g. 100.3 HEZ), breaking sends and pool/bridge init.
- Presale.contribute now resolves a signer via getSigner and passes { signer }
  to signAndSend (was signer-less -> broken for all users).
- presale.ts contribute/refund/claimVested now reject on dropped/invalid/usurped/
  retracted tx states instead of hanging the UI forever.

web/src/components/dex/XCMBridgeSetupModal.tsx

@@ -9,6 +9,7 @@ import { Button } from '@/components/ui/button';
 import { Alert, AlertDescription } from '@/components/ui/alert';
 import { useToast } from '@/hooks/use-toast';
 import { useTranslation } from 'react-i18next';
+import { parseTokenInput } from '@pezkuwi/utils/dex';
 import {
   checkBridgeStatus,
   fetchAssetHubUsdtInfo,
@@ -160,8 +161,8 @@ export const XCMBridgeSetupModal: React.FC<XCMBridgeSetupModalProps> = ({
 
     try {
       // Convert amounts to raw values (6 decimals for wUSDT, 12 for HEZ)
-      const wusdtRaw = BigInt(parseFloat(wusdtAmount) * 10 ** 6).toString();
-      const hezRaw = BigInt(parseFloat(hezAmount) * 10 ** 12).toString();
+      const wusdtRaw = parseTokenInput(wusdtAmount, 6);
+      const hezRaw = parseTokenInput(hezAmount, 12);
 
       await createWUsdtHezPool(
         assetHubApi,