fix: cursor visibility, Left/Right button nav, expand banned password chars

- Fix cursor not appearing in Certificate Details text fields (hint addstr
  was clobbering the cursor position set by place_cursor before refresh)
- Add Left/Right arrow key switching between Continue and Cancel buttons
- Expand password generation banned characters from oO01lI to oO01lIQ5S2Z8B
  (adds visually ambiguous pairs: Q/0, 5/S, 2/Z, 8/B)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

openvpncertupdate.py

@@ -154,7 +154,7 @@ def load_all_certs(pki_dir: str) -> list[CertInfo]:
 # === PASSWORD ===
 # ============================================================
 
-_BANNED_ALL       = frozenset("oO01lI")
+_BANNED_ALL       = frozenset("oO01lIQ5S2Z8B")
 _BANNED_POS2_LAST = _BANNED_ALL | frozenset("j")
 
 _UPPER            = [c for c in string.ascii_uppercase if c not in _BANNED_ALL]
@@ -636,6 +636,12 @@ def show_cert_form(
             except curses.error:
                 pass
 
+        hint = "Tab=next  F5=regen pwd  Ctrl-G=confirm  Esc=cancel"
+        try:
+            win.addstr(h - 2, 2, hint[:w - 4], curses.color_pair(COLOR_DISABLED))
+        except curses.error:
+            pass
+
         if current == _BTN_CONTINUE:
             try:
                 win.move(_BTN_Y, _btn_x_cont)
@@ -649,11 +655,6 @@ def show_cert_form(
         else:
             fields[current].place_cursor()
 
-        hint = "Tab=next  F5=regen pwd  Ctrl-G=confirm  Esc=cancel"
-        try:
-            win.addstr(h - 2, 2, hint[:w - 4], curses.color_pair(COLOR_DISABLED))
-        except curses.error:
-            pass
         win.refresh()
 
         key = win.getch()
@@ -677,6 +678,11 @@ def show_cert_form(
             )
             continue
         if current in (_BTN_CONTINUE, _BTN_CANCEL):
+            if key in (curses.KEY_LEFT, curses.KEY_RIGHT):
+                focus = active.index(
+                    _BTN_CANCEL if current == _BTN_CONTINUE else _BTN_CONTINUE
+                )
+                continue
             if key in (10, 13, curses.KEY_ENTER, ord(" ")):
                 curses.curs_set(0)
                 if current == _BTN_CONTINUE: