fix(auth): stop beforeAuthStateChanged from holding the app unstable

AngularFire wrapped beforeAuthStateChanged so that registering the
hook added a pending task, cleared only when the callback first runs.
Firebase runs that callback only on a sign-in or sign-out, so for a
visitor who does neither the app never became stable. Registered on
the server, it failed ng build during route extraction and left
server-rendered requests without a response.

This restores the blockUntilFirst: false override from #3590, which
#3613 dropped without comment while adding log-level overrides next
to it. The callback still runs inside Angular's zone and injection
context, and its returned promise still reaches Firebase, so a
rejection still cancels the sign-in. A call outside an injection
context now logs its per-call warning only at the verbose level, as
onMessage does.

Fixes #3748

Author: armando-navarro

src/auth/firebase.ts

@@ -177,6 +177,8 @@ ${exportedZoneWrappedFns}
       indexedDBLocalPersistence: null,
       prodErrorMap: null,
       multiFactor: null,
+      // Its callback fires only on a sign-in or sign-out, so blocking would keep `ApplicationRef.isStable` false.
+      beforeAuthStateChanged: { blockUntilFirst: false },
       linkWithCredential: { logLevel: LogLevel.VERBOSE },
       linkWithPhoneNumber: { logLevel: LogLevel.VERBOSE },
       linkWithPopup: { logLevel: LogLevel.VERBOSE },