Add multisig pending-operations UI, fix broken multisig address calc, new signing portal

- calculateMultisigAddress was completely broken (hex-decoded an SS58 string
  and never hashed the preimage) - fixed via @pezkuwi/util-crypto's real
  encodeMultiAddress/createKeyMulti, verified against the actual known
  multisig address on-chain.
- ReservesDashboardPage had stale Noter/Berdevk addresses that don't match
  the real signers - centralized as BRIDGE_MULTISIG_SPECIFIC_ADDRESSES.
- USDTBridge withdrawal called assets.burn directly as a single-signer
  extrinsic (always fails - only the multisig is Admin) while only
  checking status.isFinalized (a failed dispatch is still finalized, so it
  silently did nothing) - replaced with the correct transfer-to-custody
  flow the relayer actually watches for.
- New MultisigOperationsPage (/multisig/pending) lists pending calls from
  real Multisig.Multisigs storage and lets any of the 5 signers
  approve/reject with their own wallet extension.
- New standalone sign/ app (deployed separately at
  pezbridge-sign.pex.mom) - a dedicated, gated signing portal for the same
  operations, so signing isn't dependent on this app alone.

sign/src/lib/chain.ts

@@ -0,0 +1,10 @@
+import { ApiPromise, WsProvider } from '@pezkuwi/api';
+
+// Same endpoint the rest of this ecosystem's tooling (pwap-web, PezbridgeBot) uses for Pezkuwi
+// Asset Hub - the chain this multisig lives on.
+const RPC_ENDPOINT = 'wss://asset-hub-rpc.pezkuwichain.io';
+
+export function connectApi(): Promise<ApiPromise> {
+  const provider = new WsProvider(RPC_ENDPOINT);
+  return ApiPromise.create({ provider });
+}