Component button interactions (approve/deny, slash confirm, model
picker, clarify) were not checking the pairing store for authorization.
Users approved via `hermes pairing approve` could send messages and use
slash commands (which go through the gateway authz_mixin), but button
clicks were rejected because `_component_check_auth` only checked
env-var allowlists (DISCORD_ALLOWED_USERS, GATEWAY_ALLOW_ALL_USERS,
etc.) and not the pairing store.
This was a regression from commit f6f363662 which intentionally made
component auth fail-closed when no allowlist is set (security fix for
GHSA-mc26-p6fw-7pp6), but did not account for pairing-based auth.
Fix: add a `PairingStore.is_approved("discord", uid)` check to
`_component_check_auth`, mirroring `authz_mixin._check_authorization`.
The pairing store check runs after all allowlist checks, preserving the
fail-closed behavior for non-paired, non-allowed users.
Fixes#50627
7ff48a6291