deps: update golang.org/x/crypto to v0.56.0

GO-2026-6354 and GO-2026-6355 (denial of service on deadlocked SSH channels)
are reachable through the SFTP server, which listens with x/crypto/ssh.
v0.56.0 carries the fixes; govulncheck reports no reachable vulnerability.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QwirCh4nsrJCQp2WaXoVLK
Signed-off-by: Feng Ruohang <rh@vonng.com>

go.mod

@@ -118,7 +118,7 @@ require (
 	go.uber.org/zap v1.28.0
 	go.yaml.in/yaml/v3 v3.0.5
 	goftp.io/server/v2 v2.0.3
-	golang.org/x/crypto v0.55.0
+	golang.org/x/crypto v0.56.0
 	golang.org/x/oauth2 v0.36.0
 	golang.org/x/sync v0.22.0
 	golang.org/x/sys v0.47.0

go.sum

@@ -739,8 +739,8 @@ golang.org/x/crypto v0.0.0-20211209193657-4570a0811e8b/go.mod h1:IxCIyHEi3zRg3s0
 golang.org/x/crypto v0.0.0-20220315160706-3147a52a75dd/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/crypto v0.5.0/go.mod h1:NK/OQwhpMQP3MwtdjgLlYHnH9ebylxKWv3e0fK+mkQU=
 golang.org/x/crypto v0.6.0/go.mod h1:OFC/31mSvZgRz0V1QTNCzfAI1aIRzbiufJtkMIlEp58=
-golang.org/x/crypto v0.55.0 h1:+KWHjbgOaAQ66dh/YlkZKHlz9ZUlq61AFirAR9ntP8M=
-golang.org/x/crypto v0.55.0/go.mod h1:uq0V9dE/fzQuJtbnL+2EhWOE63vo164FY8xqEnV9xis=
+golang.org/x/crypto v0.56.0 h1:GUh5Ii4J5jtcseSMiRqr1jXCNHoxjeV9Fmekc2oLy6Y=
+golang.org/x/crypto v0.56.0/go.mod h1:OMW5y6CY9l38uPLmxU6l6pwcXp1obtLo3e6gT7gQR2I=
 golang.org/x/exp v0.0.0-20260820142414-ca536658362e h1:01Ju2A/fZKkci4zqx0eZxw//DnRYOnBiGJG14hFBhO8=
 golang.org/x/exp v0.0.0-20260820142414-ca536658362e/go.mod h1:zeBbvyFKDaLwa7CH/zI8KXt7gTl14SF7sO08Pl5jBCM=
 golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=