[ zapstore/zapstore ] hotfix(trust-dialog): gate trust UI by signer readiness and harden reputation lookup

In the install trust dialog, stop using profile availability as signed-in signal.
Now we show reputation details and "Always trust" only when both `activePubkey`
and `activeSigner` are available, so the UI matches actual trust persistence capability.

In reputation lookup, make the provider reactive to signer state (`watch` instead
of `read`) and send Vertex DVM params as hex pubkeys (`source` and `target`)
to avoid format issues. Also replace raw reputation errors with the user-facing
message "Service temporarily unavailable."
https://github.com/zapstore/zapstore/commit/abe89d875b3f741aa89c8cffcb0f41208ec984df