feat(clock,keyboard): alarm repeat + non-Latin keyboard alphabets

Alarm repeat (Clock Tools):
- NodePrefs::alarm_repeat_mask (weekday bitmask, struct tm::tm_wday
  convention) — new Repeat row cycles Off/Daily/Weekdays/Weekends.
  computeAlarmNextFire() scans the next 7 days for a matching weekday when
  set; evaluateAlarm() only clears alarm_on (one-shot) when the mask is
  empty, otherwise re-arms. mask==0 is byte-for-byte the original one-shot
  behaviour, so existing users see no change.

On-screen keyboard alphabets (Settings > Keyboard > Alphabet):
- KeyboardWidget reworked from single-byte ASCII cells to UTF-8 codepoints
  (insertion, backspace and T9 in-place cycling all codepoint-aware now, so a
  multi-byte character is never split) — see kbApplyCapsUtf8/kbUtf8Len/
  kbUtf8CharAt/kbUtf8LastCharBytes.
- Cyrillic, Greek and an Extended Latin set (Polish/Czech/Slovak/German/
  French/Spanish/Nordic diacritics) join the keyboard's existing #@/abc page
  cycle (Latin -> alt alphabet -> Symbols -> Latin) — no new key needed.
  NodePrefs::keyboard_alt_alphabet picks which one, if any, is active.
- Lemon font is forced on transiently inside KeyboardWidget::render() (saved
  and restored every call) whenever the alt-alphabet page is showing or
  already-typed text has non-ASCII bytes, so composing is visible even if
  Font is set to Default.
- Each script's caps-shift rule is distinct and documented in
  kbApplyCapsUtf8: flat -0x20 for ASCII/Cyrillic/Greek (with the ё/ς
  exceptions), flat -0x20 for Latin-1 (à-þ), and an adjacent-pair -1 for
  Latin Extended-A (verified against every character actually used, not a
  blanket rule for that whole Unicode block).

NodePrefs schema: two tail-appended fields this session (alarm_repeat_mask,
keyboard_alt_alphabet), SCHEMA_SENTINEL 0xC0DE001B -> 0xC0DE001D,
sizeof(NodePrefs) 2496 -> 2504 (verified via a standalone host compile).

Docs: Clock Tools' Repeat row, Settings > Keyboard > Alphabet, and the
Rooms keyboard note (no longer ASCII-only once an alphabet is enabled).

Not build-verified — no PlatformIO toolchain available this session. Caps
mappings cross-checked against Python's Unicode case tables; UTF-8 literal
bytes verified at the byte level.

docs/solo_features/clock_screen/clock_screen.md

@@ -68,11 +68,11 @@ Sensor fields show `--` when the sensor is not connected or has no data.
 
 #### Alarm
 
-A single one-shot wake alarm. Rows: **Hour**, **Minute** and **Armed**. **Enter** on Hour or Minute opens the digit editor (LEFT/RIGHT moves between the tens/units, UP/DOWN changes the digit); **Enter** on Armed toggles ON/OFF. The configured time is shown next to the **Alarm** menu row when armed, and the setting persists across reboots.
+A wake alarm with an optional repeat. Rows: **Hour**, **Minute**, **Repeat** and **Armed**. **Enter** on Hour or Minute opens the digit editor (LEFT/RIGHT moves between the tens/units, UP/DOWN changes the digit); **Enter** on Repeat cycles **Off → Daily → Weekdays → Weekends → Off**; **Enter** on Armed toggles ON/OFF. The configured time is shown next to the **Alarm** menu row when armed, and the setting persists across reboots.
 
 While an alarm is armed a bell icon signals it in two places: the top-left corner of the **Clock page** itself, and the **top status bar** of the other home pages (the status bar is hidden on the Clock page, which is why the clock face carries its own indicator). The bell is icon-only — the exact alarm time is on the **Alarm** row inside Clock Tools.
 
-The alarm is scheduled as an absolute fire instant, so it is **robust to clock re-syncs** — the mesh (every inbound packet), the companion app, GPS and the CLI can all jump the device clock at any moment. A correction that moves the clock a little still fires at the right wall-clock time; a jump that skips over the alarm time still fires (late). After firing once, the alarm disarms itself.
+The alarm is scheduled as an absolute fire instant, so it is **robust to clock re-syncs** — the mesh (every inbound packet), the companion app, GPS and the CLI can all jump the device clock at any moment. A correction that moves the clock a little still fires at the right wall-clock time; a jump that skips over the alarm time still fires (late). With **Repeat** set to Off (the default) the alarm disarms itself after firing once, same as before; with a repeat pattern set, it stays armed and re-schedules itself for the next matching day instead.
 
 The alarm only fires while the device is **awake** (it keeps running with the display off or locked). It cannot wake the device from a full **Shutdown** (the CPU and RAM are powered down), and needs a valid time source — it stays pending until the clock is synced.