feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/embedded-storage/CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+
+## Unreleased
+
+No unreleased changes yet
+
+## [0.3.1] - 2023-12-04
+
+- Let `&mut` `NorFlash` implement `NorFlash`.
+
+## [0.3.0] - 2022-02-07
+
+- Require Nor flashes error types to be convertible to generic errors.
+- Provide helper functions for Nor flashes to check for generic errors.
+- Add embedded-storage-async crate with async version of nor flash (requires nightly).
+- Add `ErrorType` trait to avoid needing to specify error type multiple times.
+
+## [0.2.0] - 2021-09-15
+
+- Removed `try_` prefix from all trait methods.
+- Add RMW helpers for Nor flashes, implementing `Storage` trait.
+
+## [0.1.0] - 2021-05-18
+
+Initial release to crates.io.
+
+[Unreleased]: https://github.com/rust-embedded-community/embedded-storage/compare/v0.3.1...HEAD
+[0.3.1]: https://github.com/rust-embedded-community/embedded-storage/releases/tag/v0.3.1
+[0.3.0]: https://github.com/rust-embedded-community/embedded-storage/releases/tag/v0.3.0
+[0.2.0]: https://github.com/rust-embedded-community/embedded-storage/releases/tag/v0.2.0
+[0.1.0]: https://github.com/rust-embedded-community/embedded-storage/releases/tag/v0.1.0