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/hash32/CHANGELOG.md

@@ -0,0 +1,65 @@
+# Change Log
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+
+## [v0.3.1] - 2022-08-09
+
+### Fixed
+
+- fixed downstream clippy warnings around `murmur3::Hasher`
+
+## [v0.3.0] - 2022-04-29
+
+### Changed
+
+- [breaking-change] Made `Hasher` a subtrait of `core::hash::Hasher`, and
+  renamed `finish` to `finish32` to avoid conflicting
+- Relaxed some restrictions on `BuildHasherDefault`
+
+### Removed
+
+- [breaking-change] Removed `Hash` in favour of `core::hash::Hash`
+- [breaking-change] Removed `BuildHasher` in favour of `core::hash::BuildHasher`
+
+## [v0.2.1] - 2021-04-19
+
+### Added
+
+- implement `Clone`, `PartialEq`, `Eq` for `BuildDefaultHasher`
+
+## [v0.2.0] - 2021-04-19
+
+### Changed
+
+- [breaking-change] `const-fn` feature has been removed
+- [breaking-change] MSRV policy has been changed to "only latest stable is guaranteed to be supported"
+
+## [v0.1.2] - 2019-11-14
+
+### Updated
+
+- Included MSRV in the documentation; also added examples for 2015 and 2018
+  editions.
+
+## [v0.1.1] - 2019-11-14
+
+### Added
+
+- Implementations for tuples
+
+## v0.1.0 - 2018-04-23
+
+Initial release
+
+[Unreleased]: https://github.com/japaric/hash32/compare/v0.3.1...HEAD
+[v0.3.1]: https://github.com/japaric/hash32/compare/v0.3.0...v0.3.1
+[v0.3.0]: https://github.com/japaric/hash32/compare/v0.2.1...v0.3.0
+[v0.2.1]: https://github.com/japaric/hash32/compare/v0.2.0...v0.2.1
+[v0.2.0]: https://github.com/japaric/hash32/compare/v0.1.2...v0.2.0
+[v0.1.2]: https://github.com/japaric/hash32/compare/v0.1.1...v0.1.2
+[v0.1.1]: https://github.com/japaric/hash32/compare/v0.1.0...v0.1.1