Use mcdsl/terminal.ReadPassword for secure password input

Replaces raw bufio.Scanner password reading (which echoed to terminal)
with the new mcdsl terminal package that suppresses echo via x/term.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.sum

@@ -1,7 +1,7 @@
 git.wntrmute.dev/mc/mc-proxy v1.2.0 h1:TVfwdZzYqMs/ksZ0a6aSR7hKGDDMG8X0Od5RIxlbXKQ=
 git.wntrmute.dev/mc/mc-proxy v1.2.0/go.mod h1:6w8smZ/DNJVBb4n5std/faye0ROLEXfk3iJY1XNc1JU=
-git.wntrmute.dev/mc/mcdsl v1.2.0 h1:41hep7/PNZJfN0SN/nM+rQpyF1GSZcvNNjyVG81DI7U=
-git.wntrmute.dev/mc/mcdsl v1.2.0/go.mod h1:lXYrAt74ZUix6rx9oVN8d2zH1YJoyp4uxPVKQ+SSxuM=
+git.wntrmute.dev/mc/mcdsl v1.3.0 h1:QYmRdGDHjDEyNQpiKqHqPflpwNJcP0cFR9hcfMza/x4=
+git.wntrmute.dev/mc/mcdsl v1.3.0/go.mod h1:MhYahIu7Sg53lE2zpQ20nlrsoNRjQzOJBAlCmom2wJc=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
@@ -74,6 +74,8 @@ golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
 golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/term v0.41.0 h1:QCgPso/Q3RTJx2Th4bDLqML4W6iJiaXFq2/ftQF13YU=
+golang.org/x/term v0.41.0/go.mod h1:3pfBgksrReYfZ5lvYM0kSO0LIkAl4Yl2bXOkKP7Ec2A=
 golang.org/x/text v0.32.0 h1:ZD01bjUt1FQ9WJ0ClOL5vxgxOI/sVCNgX1YtKwcY0mU=
 golang.org/x/text v0.32.0/go.mod h1:o/rUWzghvpD5TXrTIBuJU77MTaN0ljMWE47kxGJQ7jY=
 golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=