Register a wallet address for user-trade fanout

Binds a public 0x… address to the caller's org. When the address shows up as maker or taker on a Polymarket or Hyperliquid trade, fills are mirrored on `artery:stream:user-trade:<orgId>`. Only the public address is stored — never keys. For Polymarket, `addressType: "eoa"` (the default) takes a normal MetaMask / wallet-signer address and resolves it to the Safe / proxy that actually executes trades; pass `addressType: "safe"` to skip that lookup and store the address verbatim.