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>

docs/solo_features/settings_screen/settings_screen.md

@@ -99,7 +99,7 @@ The **repeater** mode and its flood filters live on their own screen — see **T
 | Setting  | Options    | Notes                                                                                              |
 | -------- | ---------- | -------------------------------------------------------------------------------------------------- |
 | Layout   | ABC / T9   | On-screen keyboard style. **ABC**: an a-b-c…z grid, one key per letter (the original layout). **T9**: phone-keypad multi-tap — each key is labelled with its **digit** and a letter group (e.g. `2abc`); repeated **Enter** presses cycle through the letters and then the digit itself. Applies to whichever alphabet page is active (see Alphabet below), not just Latin. |
-| Alphabet | Latin / Cyrillic / Greek / Ext.Latin | Which extra (non-Latin) alphabet, if any, joins the keyboard's page cycle. **Latin** (default): only the Latin letters and Symbols pages, as before. Any other choice adds that alphabet's own page to the same **#@/abc** key's cycle (Latin → alphabet → Symbols → Latin) — no separate key to switch scripts. **Ext.Latin** is a curated set of Polish/Czech/Slovak/German/French/Spanish/Nordic diacritics (`ą ć ę ł ń ó ś ź ż`, `č š ž`, `ä ö ü ß`, `é è ê ë ñ`, etc.), not full Unicode coverage. **Greek** covers the 24-letter alphabet plus final sigma (`ς`) but not the tonos stress accents used in proper Modern Greek spelling. Typing in the chosen alphabet needs the **Lemon** font to actually display (Settings › Display › Font) — the keyboard forces it on temporarily while that page is open even if Font is set to Default, but received messages and everything else still follow your own Font choice. |
+| Alphabet | Latin / Cyrillic / Greek / Polish / Czech / Slovak / German / French / Spanish / Portuguese / Nordic | Which extra (non-Latin) alphabet, if any, joins the keyboard's page cycle. **Latin** (default): only the Latin letters and Symbols pages, as before. Any other choice adds that alphabet's own page to the same **#@/abc** key's cycle (Latin → alphabet → Symbols → Latin) — no separate key to switch scripts. Each Latin-diacritic language (Polish, Czech, Slovak, German, French, Spanish, Portuguese, Nordic) is its own separate page with that language's full, correct set of non-ASCII letters — e.g. Czech gets `á č ď é ě í ň ó ř š ť ú ů ý ž`, German just `ä ö ü ß`. Nordic covers `å ä æ ö ø`, shared across Danish/Norwegian/Swedish since their alphabets only differ in which of those five each one uses. **Greek** covers the 24-letter alphabet plus final sigma (`ς`) but not the tonos stress accents used in proper Modern Greek spelling. Typing in the chosen alphabet needs the **Lemon** font to actually display (Settings › Display › Font) — the keyboard forces it on temporarily while that page is open even if Font is set to Default, but received messages and everything else still follow your own Font choice. |
 
 Applies to every on-screen text field (messages, waypoint labels, room passwords, preset names). Earlier releases labelled the grid *QWERTY*; the layout has always been alphabetical, so it is now named **ABC**.