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/characters/ascii.go

@@ -1,6 +1,6 @@
 package characters
 
-var invalidAsciiTable = [256]bool{
+var invalidASCIITable = [256]bool{
 	0x00: true,
 	0x01: true,
 	0x02: true,
@@ -37,6 +37,6 @@ var invalidAsciiTable = [256]bool{
 	0x7F: true,
 }
 
-func InvalidAscii(b byte) bool {
-	return invalidAsciiTable[b]
+func InvalidASCII(b byte) bool {
+	return invalidASCIITable[b]
 }