integration: add SSH check mode tests

Add ReadLog method to headscale integration container for log
inspection. Split SSH check mode tests into CLI and OIDC variants
and add comprehensive test coverage:

- TestSSHOneUserToOneCheckModeCLI: basic check mode with CLI approval
- TestSSHOneUserToOneCheckModeOIDC: check mode with OIDC approval
- TestSSHCheckModeUnapprovedTimeout: rejection on cache expiry
- TestSSHCheckModeCheckPeriodCLI: session expiry and re-auth
- TestSSHCheckModeAutoApprove: auto-approval within check period
- TestSSHCheckModeNegativeCLI: explicit rejection via CLI

Update existing integration tests to use headscale auth register.

Updates #1850

integration/cli_test.go

@@ -1100,11 +1100,11 @@ func TestNodeCommand(t *testing.T) {
 				headscale,
 				[]string{
 					"headscale",
-					"nodes",
+					"auth",
+					"register",
 					"--user",
 					"node-user",
-					"register",
-					"--key",
+					"--auth-id",
 					regID,
 					"--output",
 					"json",
@@ -1185,11 +1185,11 @@ func TestNodeCommand(t *testing.T) {
 				headscale,
 				[]string{
 					"headscale",
-					"nodes",
+					"auth",
+					"register",
 					"--user",
 					"other-user",
-					"register",
-					"--key",
+					"--auth-id",
 					regID,
 					"--output",
 					"json",
@@ -1359,11 +1359,11 @@ func TestNodeExpireCommand(t *testing.T) {
 				headscale,
 				[]string{
 					"headscale",
-					"nodes",
+					"auth",
+					"register",
 					"--user",
 					"node-expire-user",
-					"register",
-					"--key",
+					"--auth-id",
 					regID,
 					"--output",
 					"json",
@@ -1496,11 +1496,11 @@ func TestNodeRenameCommand(t *testing.T) {
 				headscale,
 				[]string{
 					"headscale",
-					"nodes",
+					"auth",
+					"register",
 					"--user",
 					"node-rename-command",
-					"register",
-					"--key",
+					"--auth-id",
 					regID,
 					"--output",
 					"json",