feat(ui): on-device channel management, remote admin tool, per-language keyboards

Messages:
- Add/edit/delete channels on-device (new ChannelsView, owned by the renamed
  MessagesScreen — was QuickMsgScreen, whose name no longer matched its scope).
  Channel secret entry supports a typed passphrase (SHA-256'd, same primitive
  the library already uses for the routing hash) or a raw 32-hex-char key.
- MyMesh::setChannelLocal() factors out the setChannel/saveChannels/
  onChannelRemoved sequence previously duplicated across the two
  CMD_SET_CHANNEL branches, shared now by the BLE and on-device paths.

Tools > Admin (new):
- Log into a repeater/room server's admin account and send CLI commands,
  the on-device equivalent of the app's repeater-admin feature.
- Commands are organised into category tabs (System/Radio/Routing/Actions)
  with common get/set fields (name, radio profile, tx power, repeat, advert
  intervals, ...) plus a free-text "Custom command..." fallback for anything
  else. A field row fetches the current value, opens it pre-filled for
  editing, and sends the change — falling back to a blank editor if the
  fetch fails or times out.
- The admin password persists and self-heals exactly like room logins in
  Messages: saved on a confirmed admin-level login, forgotten on a failed
  one, left alone if merely under-privileged.
- New MyMesh::sendAdminCommand()/AbstractUITask::onAdminReply() plumbing so
  a reply reaches the UI without touching the existing BLE/app CLI-terminal
  path (queueMessage's should_display gate is untouched).

Shared TabBar.h extracted from NearbyScreen/BotScreen's independently
duplicated tab-carousel rendering (now a third consumer via Admin) — also
fixes neighbouring tabs vanishing outright when they didn't fully fit;
they now truncate with an ellipsis instead.

Keyboard: the combined "Ext.Latin" alphabet split into 8 separate,
linguistically complete per-language keyboards (Polish, Czech, Slovak,
German, French, Spanish, Portuguese, Nordic), and fixed an OLED-only bug
where tall accented glyphs overlapped the keyboard's separator line
(SH1106's Lemon-font ascent constant was 2-3px short for them).

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

examples/companion_radio/ui-new/ToolsScreen.h

@@ -14,7 +14,7 @@ class ToolsScreen : public UIScreen {
 
   enum Action {
     ACT_NEARBY, ACT_LIVESHARE, ACT_TRAIL, ACT_LOCATOR, ACT_COMPASS,
-    ACT_BOT, ACT_AUTOADVERT, ACT_REPEATER,
+    ACT_BOT, ACT_AUTOADVERT, ACT_REPEATER, ACT_ADMIN,
     ACT_CLOCK, ACT_RINGTONE, ACT_DIAGNOSTICS
   };
   struct Tool { const char* label; const MiniIcon* icon; Action action; };
@@ -49,6 +49,7 @@ class ToolsScreen : public UIScreen {
       case ACT_BOT:         _task->gotoBotScreen();         break;
       case ACT_AUTOADVERT:  _task->gotoAutoAdvertScreen();  break;
       case ACT_REPEATER:    _task->gotoRepeaterScreen();    break;
+      case ACT_ADMIN:       _task->gotoAdminScreen();       break;
       case ACT_CLOCK:       _task->gotoClockTools();        break;
       case ACT_RINGTONE:    _task->gotoRingtoneEditor();    break;
       case ACT_DIAGNOSTICS: _task->gotoDiagnosticsScreen(); break;
@@ -121,6 +122,7 @@ const ToolsScreen::Tool ToolsScreen::COMMS_TOOLS[] = {
   { "Auto-Reply Bot", &ICON_BOT,      ACT_BOT },
   { "Auto-Advert",    &ICON_ADVERT,   ACT_AUTOADVERT },
   { "Repeater",       &ICON_REPEATER, ACT_REPEATER },
+  { "Admin",          &ICON_GEAR,     ACT_ADMIN },
 };
 const ToolsScreen::Tool ToolsScreen::SYSTEM_TOOLS[] = {
   { "Clock Tools",     &ICON_ALARM, ACT_CLOCK },
@@ -129,6 +131,6 @@ const ToolsScreen::Tool ToolsScreen::SYSTEM_TOOLS[] = {
 };
 const ToolsScreen::Section ToolsScreen::SECTIONS[] = {
   { "Location", &ICON_MAP_CONTACT, LOCATION_TOOLS, 5 },
-  { "Comms",    &ICON_ADVERT,      COMMS_TOOLS,    3 },
+  { "Comms",    &ICON_ADVERT,      COMMS_TOOLS,    4 },
   { "System",   &ICON_GEAR,        SYSTEM_TOOLS,   3 },
 };