Simplify the transports cast in /passkeys/registration/begin

The cast on `p.transports` was a multi-line conditional-types
expression that fished the element type out of
buildRegistrationOptions' parameter shape via `Parameters<...>`
and `infer T`.  The element type is just
AuthenticatorTransportFuture from @simplewebauthn/server, which
the same file already imports transitively, so import it
directly and cast to AuthenticatorTransportFuture[].  Runtime is
identical; the call site fits on one line again.

#487 (comment)

Assisted-by: Claude Code:claude-opus-4-7

Author: dahlia

src/pages/auth.tsx

@@ -1,5 +1,6 @@
 import { zValidator } from "@hono/zod-validator";
 import { getLogger } from "@logtape/logtape";
+import type { AuthenticatorTransportFuture } from "@simplewebauthn/server";
 import { eq } from "drizzle-orm";
 import { Hono } from "hono";
 import { deleteCookie, getSignedCookie, setSignedCookie } from "hono/cookie";
@@ -116,13 +117,7 @@ auth.post("/passkeys/registration/begin", async (c) => {
     email: credential.email,
     existingCredentials: enrolled.map((p) => ({
       id: p.id,
-      transports: p.transports as ReadonlyArray<
-        Parameters<
-          typeof buildRegistrationOptions
-        >[0]["existingCredentials"][number]["transports"]
-      > extends ReadonlyArray<infer T>
-        ? T
-        : never,
+      transports: p.transports as AuthenticatorTransportFuture[],
     })),
   });
   const expiresAt = Date.now() + PASSKEY_REG_MAX_AGE_SECONDS * 1000;