Use mcdsl/terminal for all password prompts

Replace direct golang.org/x/term calls with mcdsl/terminal.ReadPassword
across mciasctl (6 sites), mciasgrpcctl (1 site), and mciasdb (1 site).
Aligns with the new CLI security standard in engineering-standards.md.

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

vendor/google.golang.org/grpc/dialoptions.go

@@ -608,6 +608,8 @@ func WithChainStreamInterceptor(interceptors ...StreamClientInterceptor) DialOpt
 
 // WithAuthority returns a DialOption that specifies the value to be used as the
 // :authority pseudo-header and as the server name in authentication handshake.
+// This overrides all other ways of setting authority on the channel, but can be
+// overridden per-call by using grpc.CallAuthority.
 func WithAuthority(a string) DialOption {
 	return newFuncDialOption(func(o *dialOptions) {
 		o.authority = a