Add build verification and test credential checking

- Build script now shows summary of embedded credentials after build
- quick-test.sh now checks if binary has credentials before running
- This prevents the "dial tcp :143" empty server error

Tests if help output shows empty string in default values.

build.sh

@@ -135,6 +135,32 @@ go build \
   -o ~/bin/nextcloud-mail
 echo "✓ nextcloud-mail built successfully"
 
+# Verification: Show what credentials were embedded
+echo ""
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo "  Build Verification Summary"
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo "  IMAP Server: $IMAP_SERVER"
+echo "  IMAP Port: $IMAP_PORT"
+echo "  IMAP Username: $IMAP_USER"
+echo "  IMAP Password: [$(echo "$IMAP_PASS" | sed 's/./*/g')]"
+echo "  SMTP Server: $SMTP_SERVER"
+echo "  SMTP Port: $SMTP_PORT"
+echo "  SMTP Username: $SMTP_USER"
+echo "  SMTP Password: [$(echo "$SMTP_PASS" | sed 's/./*/g')]"
+echo "  Use SSL: $USE_SSL"
+echo "  Ignore Certs: $IGNORE_CERTS"
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo ""
+
+if [ -z "$IMAP_USER" ] || [ -z "$IMAP_PASS" ]; then
+  echo "⚠️  Warning: IMAP username or password appears to be empty!"
+  echo "   The binary was built but may not work correctly."
+  echo "   If this is incorrect, please rebuild with valid credentials."
+fi
+
+echo ""
+
 echo ""
 echo "All tools built successfully!"
 echo ""