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/esp-println/CHANGELOG.md

@@ -0,0 +1,63 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+### Changed
+
+### Fixed
+
+### Removed
+
+## 0.12.0 - 2024-10-10
+
+### Changed
+
+- Replace environment variables `ESP_LOGLEVEL` and `ESP_LOGFILTER` with just one environment variable: `ESP_LOG` (#2291)
+
+## 0.11.0 - 2024-08-29
+
+### Added
+
+- Made `esp_println::Printer::write_bytes` public (#1812)
+
+## 0.10.0 - 2024-07-15
+
+### Added
+
+- Add `auto` feature to auto-detect Serial-JTAG/UART communication (#1658)
+
+### Changed
+
+- `auto` is the default communication method (#1658)
+- Add the `links` field to Cargo.toml so that only one version of the package can be included (#1761)
+
+## 0.9.1 - 2024-03-11
+
+### Changed
+
+- Un-pinned the defmt package's version number
+
+## 0.9.0 - 2024-02-07
+
+### Added
+
+- Add support for ESP32-P4
+
+### Removed
+
+- Remove ESP 8266 support
+
+## 0.8.0 - 2023-12-21
+
+### Removed
+
+- Remove RTT and defmt-raw support
+
+[Unreleased]: https://github.com/esp-rs/esp-hal/commits/main/esp-println?since=2024-10-10