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/enum-as-inner/CHANGELOG.md

@@ -0,0 +1,73 @@
+# Change Log: enum-as-inner
+
+All notable changes to this project will be documented in this file.
+This project adheres to [Semantic Versioning](http://semver.org/).
+
+## 0.6.0
+
+- Previous changes deserved a minor version bump, 0.5.2 yanked, 0.6.0 released
+
+## 0.5.2
+
+- Add is_* impl for non unit variants, #91 by goolmoos
+- Fully qualify both Option and Result in generated code, #96 by kepler-5
+
+## 0.5.1
+
+- Generated functions now marked `#[inline]` to help with lto across crate boundaries for libraries, #87 by zxch3n
+
+## 0.5.0
+
+- Changed all references in generated functions to use `Self` where applicable.
+
+## 0.4.0
+
+### Changed
+
+- Change unit variants to use predicate functions (@CeleritasCelery) #76
+
+## 0.3.4
+
+### Changed
+
+- updated `heck` to 0.4 #82
+
+## 0.3.3
+
+### Added
+
+- Support for Generic enum members (@Jan561) #19
+
+## 0.3.2
+
+### Added
+
+- Added `as_mut_*` for mutable access to inners (@yuyoyuppe) #14
+
+## 0.3.1
+
+### Added
+
+- this CHANGELOG.md
+
+### Changes
+
+- Updated docs for new `use` syntax of macros
+
+## 0.3
+
+### Changes
+
+- Upgrade to work with 1.0 versions of proc-macro2, quote, and syn
+
+## 0.2
+
+### Fixes
+
+- some bug fixes for edge conditions
+
+## 0.1
+
+### Added
+
+- first release