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/byte-slice-cast/CHANGELOG.md

@@ -0,0 +1,105 @@
+# 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),
+specifically the [variant used by Rust](http://doc.crates.io/manifest.html#the-version-field).
+
+## [1.2.3] - 2025-03-03
+### Changed
+- Fix tests for Rust 1.81.
+- Declare Rust 1.51 as MSRV.
+
+## [1.2.2] - 2022-10-28
+### Changed
+- Fix a couple of clippy warnings in the tests.
+
+## [1.2.1] - 2022-02-25
+### Changed
+- Make trait methods `#[inline]`. This allows the compiler to make the call a
+  no-op in many cases.
+
+## [1.2.0] - 2021-10-19
+### Added
+- Trait impls for converting between `&[[T; N]]` and `&[u8]` for specific `T`.
+
+## [1.1.0] - 2021-09-16
+### Added
+- `ToByteSlice` and `ToMutByteSlice` impl for `&[()]`. This always produces an
+  empty byte slice.
+
+## [1.0.0] - 2020-10-13
+### Removed
+- Support for casting between `Vec<T>` and `Vec<u8>`. This was actually
+  unsound as the alloc trait requires that memory is deallocated with exactly
+  the same alignment as it was allocated with.
+
+### Fixed
+- `usize` tests on 16/32 bit architectures.
+
+### Changed
+- Various documentation improvements.
+
+## [0.3.5] - 2019-12-22
+### Changed
+- Improve documentation and examples
+
+### Fixed
+- Fix running of tests on 16/32 bit architectures
+
+## [0.3.4] - 2019-11-11
+### Added
+- Support for casting between `Vec<T>` and `Vec<u8>`
+
+## [0.3.3] - 2019-11-02
+### Added
+- Support for `usize` and `isize`
+
+## [0.3.2] - 2019-07-26
+### Changed
+- Add `no_std` support
+- Migrate to 2018 edition
+
+## [0.3.1] - 2019-06-05
+### Fixed
+- Casting of empty slices works correctly now instead of failing with an
+  alignment mismatch error.
+
+## [0.3.0] - 2019-05-11
+### Added
+- The `Error` type now implements `Clone`.
+
+### Changed
+- `AsByteSlice::as_byte_slice` and `ToByteSlice::to_byte_slice` were changed
+  to always return `&[u8]` instead of `Result<&[u8], Error>`.
+- `AsMutByteSlice::as_mut_byte_slice` and `ToMutByteSlice::to_mut_byte_slice`
+  were changed to always return `&mut [u8]` instead of `Result<&mut [u8],
+  Error>`.
+- The `Display` impl for `Error` now produces more detailed error messages.
+- The variants of the `Error` enum were renamed.
+
+## [0.2.0] - 2018-06-01
+### Changed
+- Major refactoring of how the traits work. It is now possible to work
+  directly on `AsRef<[T]>` and `AsMut<[T]>`, e.g. on `Vec<T>` and `Box<[T]>`.
+
+### Added
+- Trait impls for i128 and u128.
+
+## [0.1.0] - 2017-08-14
+- Initial release of the `byte-slice-cast` crate.
+
+[Unreleased]: https://github.com/sdroege/byte-slice-cast/compare/1.2.3...HEAD
+[1.2.3]: https://github.com/sdroege/byte-slice-cast/compare/1.2.2...1.2.3
+[1.2.2]: https://github.com/sdroege/byte-slice-cast/compare/1.2.1...1.2.2
+[1.2.1]: https://github.com/sdroege/byte-slice-cast/compare/1.2.0...1.2.1
+[1.2.0]: https://github.com/sdroege/byte-slice-cast/compare/1.1.0...1.2.0
+[1.1.0]: https://github.com/sdroege/byte-slice-cast/compare/1.0.0...1.1.0
+[1.0.0]: https://github.com/sdroege/byte-slice-cast/compare/0.3.5...1.0.0
+[0.3.5]: https://github.com/sdroege/byte-slice-cast/compare/0.3.4...0.3.5
+[0.3.4]: https://github.com/sdroege/byte-slice-cast/compare/0.3.3...0.3.4
+[0.3.3]: https://github.com/sdroege/byte-slice-cast/compare/0.3.2...0.3.3
+[0.3.2]: https://github.com/sdroege/byte-slice-cast/compare/0.3.1...0.3.2
+[0.3.1]: https://github.com/sdroege/byte-slice-cast/compare/0.3.0...0.3.1
+[0.3.0]: https://github.com/sdroege/byte-slice-cast/compare/0.2.0...0.3.0
+[0.2.0]: https://github.com/sdroege/byte-slice-cast/compare/0.1.0...0.2.0