Schedule Selector

[amah853]

This pull request adds support for locally overriding today's schedule, allowing users to select a different schedule for the current day via the settings UI. Several internal changes support these features, including a newScheduleOverrideManager and updates to UI components.

Local Schedule Override Functionality

• Added a new ScheduleOverrideManager (src/ScheduleOverrideManager.ts) to manage local schedule overrides, including persisting overrides, loading them on startup, and cleaning up old entries.
• Updated Calendar and BellTimer2 to check for and apply local schedule overrides when determining the current schedule. [1] [2] [3] [4]
• Enhanced the settings UI to allow users to select and save a schedule override for today, with options loaded dynamically and changes persisted locally. [1] [2] [3] [4]

User Interface Improvements

• Modified the schedule display to prepend "Unsynced |" when a local override is active, making it clear to users when the displayed schedule differs from the default.
• Improved settings UI descriptions and layout for clarity.

Closes: #122

[amah853]

@nicolaschan this is ready for review

[amah853]

@nicolaschan any updates on this PR? thanks.