swarm-queue-client: request the bearer-authz scope when minting an agent token

`swarm-logs query` got a bare nginx 401 from the swarm log store on every
query. The agent OIDC client is registered for `authelia.bearer.authz`
(`swarm-authelia.nix`'s `agentClients` sets `bearerAuthz`), but registration
is not issuance: the token request asked for no scope, so the token came back
carrying none, and authelia's `/api/authz/auth-request` refuses that exactly
as it refuses an unauthenticated caller.

The same failure is already recorded in `swarm-otel.nix` against the
collector's client, on the same scope string — prometheus asks for no scopes
unless told to, and every scrape was refused at introspection. This is that
bug one layer down, so it gets the same shape of fix.

`scope` becomes an opt-in parameter alongside `audience`, not a hardcoded
value or a config field: the two travel together (registered ≠ requested
applies to both) and only the destination decides whether either is needed.
`None` keeps every other caller byte-identical — the NATS connect callback,
`auth.rs`'s bridge client and the OTLP push client all pass it.

Refs #4464

swarm-controller/src/auth.rs

@@ -98,7 +98,7 @@ impl AuthBridge {
         // configured CA, if any) — deliberately not `self.http`, which is
         // the bridge's own client and has nothing to do with authelia's
         // token endpoint's trust anchors.
-        let token = swarm_queue_client::mint_token_for(&self.queue_cfg, None)
+        let token = swarm_queue_client::mint_token_for(&self.queue_cfg, None, None)
             .await
             .context("minting a bearer token for swarm-authelia-bridge")?;