Relay pass (PC side): keep the retry for an unchanged account, and never let a hanging pass setup hold pairing #3277

Follow-up from the review of #3272 (fixes #3271, relay pass PC side) at head 8689dfc. No HIGH; two of #3271's fixes are partial (reproduced in memory):

1. Naming the same account again still re-requests a refused pass (server/relay/service.ts:216). With no pass held (e.g. after 409 relay_limit scheduled a 30-minute retry), each nine-minute Add this PC relist cancels that schedule and asks again. Keep the scheduled retry when the account is unchanged.
2. A pass-setup request that hangs still gates pairing (src/lib/account/addThisPc.ts:37). With the relay not enforcing, a directory listing that succeeds followed by a never-settling /api/account/relay-account leaves listThisPc pending, so the UI never enters its pairing wait. Bound it with a timeout, or don't await it before the pairing wait.