payment-service classifies network failures by message text, same shape as the send bug

[TortoiseWolfe]

src/lib/payments/payment-service.ts:128-133 has the same structure as the message-send bug fixed in #98:

error.message.includes('fetch') || error.message.includes('network') || error.message.includes('ECONNREFUSED')

…deciding whether to queueOperation. It is a PostgREST .insert().select().single() (:118-122) whose status is available and discarded, exactly as on the send path before #98.

Two consequences, both demonstrated on the messaging side:

1. WebKit is not covered. Safari reports an aborted fetch as TypeError: Load failed, which matches none of those three substrings. So on Safari a payment that fails at the transport layer is not queued.
2. No structural guard. A Postgres rejection whose message happens to contain "network" would be misread as a transport failure. fix(messaging): stop discarding the user's message when a send fails #98 addressed this by gating on the PostgREST code (a rejection always carries a SQLSTATE; a fetch failure carries code: '' and status: 0) and by threading the original through as cause so wrapping does not lose it.

Not folded into #98 deliberately — that PR is already broad and touches a different service. The fix is the same shape and should be small: reuse the looksLikeFetchFailure + code-gate approach, or capture status === 0 at the destructure.

Worth checking whether payments has an equivalent of the third bug too: does a failed payment discard user input the way the message composer did?