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/git.wntrmute.dev/mc/mcdsl/terminal/terminal.go

@@ -0,0 +1,36 @@
+// Package terminal provides secure terminal input helpers for CLI tools.
+package terminal
+
+import (
+	"fmt"
+	"os"
+
+	"golang.org/x/term"
+)
+
+// ReadPassword prints the given prompt to stderr and reads a password
+// from the terminal with echo disabled. It prints a newline after the
+// input is complete so the cursor advances normally.
+func ReadPassword(prompt string) (string, error) {
+	b, err := readRaw(prompt)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}
+
+// ReadPasswordBytes is like ReadPassword but returns a []byte so the
+// caller can zeroize the buffer after use.
+func ReadPasswordBytes(prompt string) ([]byte, error) {
+	return readRaw(prompt)
+}
+
+func readRaw(prompt string) ([]byte, error) {
+	fmt.Fprint(os.Stderr, prompt)
+	b, err := term.ReadPassword(int(os.Stdin.Fd())) //nolint:gosec // fd fits in int
+	fmt.Fprintln(os.Stderr)
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
+}