BaseUI: Autosave Messages

[HarukiToreda]

This PR adds message autosaving to the node.

Previously, messages were only saved to flash when the user manually shut down or restarted the device using the UI. If the node lost power or the reset button was pressed, all messages stored in RAM were lost.

With this change, messages are automatically saved to flash every 2 hours. The 2 hour interval was chosen to reduce flash wear, especially on nRF52 based devices where flash has a limited write lifespan. There is a manual overwrite to this interval that can be applied to other nodes like esp32 ex. -DMESSAGE_AUTOSAVE_INTERVAL_SEC=3600

Behavior

• The autosave timer does not start on boot
• The timer starts when the first new message is received
• All messages received since the last save are marked as unsaved
• When the 2 hour interval is reached, unsaved messages are written to flash
• The autosave cadence continues automatically until reboot
• If no new messages are received during an interval, the save is skipped and no flash write occurs
• Deleting messages will also skip saving

This ensures messages survive unexpected power loss while keeping flash writes to a minimum.

[Copilot]

Pull request overview

This PR implements autosave functionality for messages stored in device RAM. Previously, messages were only persisted to flash during manual shutdown/restart, resulting in data loss during unexpected power failures or reset button usage. The new feature automatically saves unsaved messages to flash at a configurable interval (intended to be 12 hours by default), with special logic to avoid unnecessary flash writes when no new messages have been received.

Changes:

• Added autosave timer mechanism that triggers periodic saves of unsaved messages
• Integrated autosave tick call into the main event loop
• Refactored message menu to consolidate delete operations into a submenu
• Added state tracking for unsaved messages and automatic persistence

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/main.cpp	Added MessageStore.h include and messageStoreAutosaveTick() call in main loop
src/graphics/draw/MenuHandler.cpp	Refactored message response menu to use DeleteMenu enum and removed duplicate delete logic
src/MessageStore.h	Added messageStoreAutosaveTick() function declaration with appropriate guards
src/MessageStore.cpp	Implemented core autosave logic including interval calculation, state tracking, and integration with add/save/load operations