feat(keyboard): selectable main/additional script for the on-screen keyboard

Page 0 was hardcoded to Latin -- Cyrillic/Greek could only ever be the
second, cycled-to page. Settings > Keyboard's Alphabet row splits into
Main (which script the keyboard opens on by default) and Additional
(the second one reached via #@/abc), so a Cyrillic/Greek typist can make
their own script the default instead of always landing on Latin first.
Setting Additional equal to Main collapses back to a 2-page cycle (that
script + Symbols), same rule the old Latin-hardcoded design already used
implicitly.

KeyboardWidget.h: cellStr()/t9GroupStr() now dispatch through
scriptCellStr()/scriptT9GroupStr(), treating Latin as an ordinary peer of
Cyrillic/Greek instead of a special case; scriptHint() replaces
altAlphabetHint() so the #@/abc key's "next page" hint is correct
regardless of which script that lands on; the accent popup's gating
checks the current page's actual script instead of assuming page 0 is
always Latin. Removed the now-dead pageIsAltAlphabet().

NodePrefs gains keyboard_main_alphabet (schema sentinel 0xC0DE001F ->
0xC0DE0020, same append-at-tail/clamp-on-load pattern as every prior
schema growth this file uses). Verified via a real build that the new
field lands in existing tail padding -- sizeof(NodePrefs) is unchanged
at 2712.

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

release-notes.md

@@ -6,7 +6,7 @@
 - **On-device channel management.** Messages › Channels gets a **"+ Add channel"** row and per-channel **Edit**/**Delete** — create or join a channel by typing either a passphrase (hashed to the channel secret, same idea as a room password) or the exact 32-hex-character key from a channel QR code. No phone app required.
 - **Tools › Admin — administer a remote repeater/room from the device.** Log into a node you have admin rights on (same self-healing saved-password handshake as room logins) and browse its settings in category tabs — **System** (name, owner info), **Radio** (Frequency/Bandwidth/Spreading factor/Coding rate/TX power), **Routing** (Repeat/Advert interval/Flood advert interval/Max hops), **Actions** (reboot, send advert, sync clock, …) — plus a free-text **Custom command…** escape hatch (with **{}**-key command-name completion) for anything not covered. Radio and Routing fields use a type-appropriate editor instead of raw text — a digit-cursor for Frequency (the same widget Settings' own Radio screen uses locally), discrete-set stepping for Bandwidth/Spreading factor/Coding rate, plain number steppers for the rest, and an ON/OFF toggle for Repeat — adjusting a value costs no mesh traffic until you actually confirm it with **Enter** (**Cancel** sends nothing). Reachable either from **Tools › Admin** (opens the same Nodes list to pick a target) or directly via a repeater/room's own **Hold Enter › Admin** action.
 - **Auto-Reply Bot gains a third target: room servers**, alongside DM and Channel, with its own trigger/reply/commands — the screen is redesigned as a circular tab carousel (**Direct/Channel/Room/Other**, **LEFT/RIGHT** to switch, **UP/DOWN** within a tab) instead of one long list. Each target's **Enable** and **Commands** toggle is now fully independent (they used to secretly share the DM tab's setting for Channel/Room too). New `{name}`/`{hops}` reply placeholders, a DM allow-list (all chat contacts or favourites only), and a dedicated stepper for Quiet Hours.
-- **Keyboard: accent popup, better editing.** Holding **Enter** on a Latin letter with accented variants (`a c d e i l n o r s t u y z`) now opens a one-row popup of that letter's accents — e.g. holding `a` offers `á à â ã ä å ą` — covering every European Latin-diacritic letter (Polish, Czech, Slovak, German, French, Spanish, Portuguese, Nordic, …) from one popup instead of a separate page per language; **Cyrillic**/**Greek** remain full alt-alphabet pages under **Settings › Keyboard › Alphabet**. Shift is now **one-shot** by default (capitalises just the next letter; **Hold Enter** on Shift toggles the old sticky caps-lock back on), **Hold Enter** on Backspace clears the whole field, and **UP** from the top letter row enters a cursor-positioning mode (**LEFT/RIGHT** move; **UP/DOWN** jump to start/end, then continue on to the special row / letter grid if pressed again once already there) so you can edit or insert anywhere in what you've typed, not just at the end.
+- **Keyboard: accent popup, selectable main script, better editing.** Holding **Enter** on a Latin letter with accented variants (`a c d e i l n o r s t u y z`) now opens a one-row popup of that letter's accents — e.g. holding `a` offers `á à â ã ä å ą` — covering every European Latin-diacritic letter (Polish, Czech, Slovak, German, French, Spanish, Portuguese, Nordic, …) from one popup instead of a separate page per language. **Settings › Keyboard** splits **Alphabet** into **Main** and **Additional**: Main picks which script (Latin/Cyrillic/Greek) the keyboard opens on by default, Additional picks the second one reached via the **#@/abc** cycle key — so a Cyrillic or Greek typist can make their own script the default instead of always landing on Latin first. Shift is now **one-shot** by default (capitalises just the next letter; **Hold Enter** on Shift toggles the old sticky caps-lock back on), **Hold Enter** on Backspace clears the whole field, and **UP** from the top letter row enters a cursor-positioning mode (**LEFT/RIGHT** move; **UP/DOWN** jump to start/end, then continue on to the special row / letter grid if pressed again once already there) so you can edit or insert anywhere in what you've typed, not just at the end.
 - **Messages get a messenger-style history.** History bubbles are now sized to their content and anchored **right** (outgoing) / **left** (incoming); the list runs **newest at the bottom**, growing upward as you scroll into the past; the **[+ send]** compose button moved to the right edge to match.
 - **Clock Tools: alarm repeat.** The Alarm screen gains a **Repeat** row (Off/Daily/Weekdays/Weekends) — Hour/Minute merge into one **Time** row edited with an HH:MM digit cursor, and **Repeat**/**Armed** now respond to **LEFT/RIGHT** like every other Settings field instead of Enter-only.
 - **Diagnostics becomes a tab carousel** (Live/System/Font): **System** adds firmware version + build date, device model and the active radio parameters; **Font** is a rendering test card with one sample line per script the on-device font covers, so coverage can be eyeballed directly.