show email alongside CN in TUI main menu cert list

CertInfo.email was already populated from index.txt but never
rendered; add it as a fixed-width column next to CN in the cert
list rows (blank when unknown).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

openvpncertupdate.py

@@ -938,7 +938,7 @@ def show_main_screen(
                 cert = certs[i]
                 box  = "[X]" if cert.cn in checked else "[ ]"
                 lbl  = _expiry_label(cert)
-                line = f"  {box} {lbl:<18} {cert.cn}"
+                line = f"  {box} {lbl:<18} {cert.cn:<20} {cert.email}"
                 try:
                     stdscr.addstr(row_y, 0, line.ljust(sw - 1)[:sw - 1], sel_attr)
                 except curses.error: