# Clock Persistence, Size Setting, and Timezone Support

## Task Description
Implemented the plan from `clock_settings_and_timezone_fd0bf03f.plan.md` covering three features:
1. Fix homeScreenClock setting not persisting across reboots
2. Add clock size setting (Small/Medium/Large)
3. Add timezone selection with North American presets and custom UTC offset

## Changes Made

### 1. Fix Persistence Bug
- **`src/CrossPointSettings.cpp`**: Removed stale legacy `sleepScreenGradientDir` read (lines 270-271) from `loadFromFile()` that was causing a one-byte deserialization offset, corrupting `preferredPortrait`, `preferredLandscape`, and `homeScreenClock`.

### 2. Clock Size Setting
- **`src/CrossPointSettings.h`**: Added `CLOCK_SIZE` enum (SMALL/MEDIUM/LARGE) and `uint8_t clockSize` field.
- **`src/CrossPointSettings.cpp`**: Added `clockSize` to `writeSettings()` and `loadFromFile()` serialization.
- **`src/SettingsList.h`**: Added clock size enum setting in Display category.
- **`lib/I18n/I18nKeys.h`**: Added `STR_CLOCK_SIZE`, `STR_CLOCK_SIZE_SMALL`, `STR_CLOCK_SIZE_MEDIUM`, `STR_CLOCK_SIZE_LARGE`.
- **All 8 YAML translation files**: Added clock size strings.
- **`src/components/themes/BaseTheme.cpp`** and **`src/components/themes/lyra/LyraTheme.cpp`**: Updated `drawHeader()` to select font (SMALL_FONT_ID / UI_10_FONT_ID / UI_12_FONT_ID) based on `clockSize` setting.

### 3. Timezone Support
- **`src/CrossPointSettings.h`**: Added `TIMEZONE` enum (UTC, Eastern, Central, Mountain, Pacific, Alaska, Hawaii, Custom), `uint8_t timezone` and `int8_t timezoneOffsetHours` fields, and `getTimezonePosixStr()` declaration.
- **`src/CrossPointSettings.cpp`**: Added timezone/offset serialization, validation (-12 to +14), and `getTimezonePosixStr()` implementation returning POSIX TZ strings (including DST rules for NA timezones).
- **`lib/I18n/I18nKeys.h`** + **all YAML files**: Added timezone strings and "Set UTC Offset" label.
- **`src/SettingsList.h`**: Added timezone enum setting in Display category.
- **`src/activities/settings/SetTimezoneOffsetActivity.h/.cpp`** (new files): UTC offset picker activity (-12 to +14), using same UI pattern as `SetTimeActivity`.
- **`src/activities/settings/SettingsActivity.h`**: Added `SetTimezoneOffset` to `SettingAction` enum.
- **`src/activities/settings/SettingsActivity.cpp`**: Added include, action entry, handler for SetTimezoneOffset, and `setenv`/`tzset` call after every settings save.
- **`src/main.cpp`**: Apply saved timezone via `setenv`/`tzset` on boot after `SETTINGS.loadFromFile()`.
- **`src/util/TimeSync.cpp`**: Apply timezone before starting NTP sync so time displays correctly.

## Build Status
Firmware builds successfully (99.5% flash usage).

## Follow-up Items
- Test on device: verify clock persistence, size changes, timezone selection, and custom UTC offset picker.
- Timezone strings use English fallbacks for non-English languages.