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/github.com/pelletier/go-toml/v2/internal/tracker/key.go

@@ -36,7 +36,7 @@ func (t *KeyTracker) Pop(node *unstable.Node) {
 	}
 }
 
-// Key returns the current key
+// Key returns the current key.
 func (t *KeyTracker) Key() []string {
 	k := make([]string, len(t.k))
 	copy(k, t.k)