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/embassy-executor/CHANGELOG.md

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+# 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
+
+## 0.6.3 - 2024-11-12
+
+- Building with the `nightly` feature now works with the Xtensa Rust compiler 1.82.
+- Compare vtable address instead of contents. Saves 44 bytes of flash on cortex-m.
+
+## 0.6.2 - 2024-11-06
+
+- The `nightly` feature no longer requires `nightly-2024-09-06` or newer.
+
+## 0.6.1 - 2024-10-21
+
+- Soundness fix: Deny using `impl Trait` in task arguments. This was previously accidentally allowed when not using the `nightly` feature,
+  and could cause out of bounds memory accesses if spawning the same task mulitple times with different underlying types
+  for the `impl Trait`. Affected versions are 0.4.x, 0.5.0 and 0.6.0, which have been yanked.
+- Add an architecture-agnostic executor that spins waiting for tasks to run, enabled with the `arch-spin` feature.
+- Update for breaking change in the nightly waker_getters API. The `nightly` feature now requires `nightly-2024-09-06` or newer.
+- Improve macro error messages.
+
+## 0.6.0 - 2024-08-05
+
+- Add collapse_debuginfo to fmt.rs macros.
+- initial support for AVR
+- use nightly waker_getters APIs
+
+## 0.5.1 - 2024-10-21
+
+- Soundness fix: Deny using `impl Trait` in task arguments. This was previously accidentally allowed when not using the `nightly` feature,
+  and could cause out of bounds memory accesses if spawning the same task mulitple times with different underlying types
+  for the `impl Trait`. Affected versions are 0.4.x, 0.5.0 and 0.6.0, which have been yanked.
+
+## 0.5.0 - 2024-01-11
+
+- Updated to `embassy-time-driver 0.1`, `embassy-time-queue-driver 0.1`, compatible with `embassy-time v0.3` and higher.
+
+## 0.4.0 - 2023-12-05
+
+- Removed `arch-xtensa`. Use the executor provided by the HAL crate (`esp-hal`, `esp32s3-hal`, etc...) instead.
+- Added an arena allocator for tasks, allowing using the `main` and `task` macros on Rust 1.75 stable. (it is only used if the `nightly` feature is not enabled. When `nightly` is enabled, `type_alias_impl_trait` is used to statically allocate tasks, as before).
+
+## 0.3.3 - 2023-11-15
+
+- Add `main` macro reexport for Xtensa arch.
+- Remove use of `atomic-polyfill`. The executor now has multiple implementations of its internal data structures for cases where the target supports atomics or doesn't.
+
+## 0.3.2 - 2023-11-06
+
+- Use `atomic-polyfill` for `riscv32`
+- Removed unused dependencies (static_cell, futures-util)
+
+## 0.3.1 - 2023-11-01
+
+- Fix spurious "Found waker not created by the Embassy executor" error in recent nightlies.
+
+## 0.3.0 - 2023-08-25
+
+- Replaced Pender. Implementations now must define an extern function called `__pender`.
+- Made `raw::AvailableTask` public
+- Made `SpawnToken::new_failed` public
+- You can now use arbitrary expressions to specify `#[task(pool_size = X)]`
+
+## 0.2.1 - 2023-08-10
+
+- Avoid calling `pend()` when waking expired timers
+- Properly reset finished task state with `integrated-timers` enabled
+- Introduce `InterruptExecutor::spawner()`
+- Fix incorrect critical section in Xtensa executor
+
+## 0.2.0 - 2023-04-27
+
+- Replace unnecessary atomics in runqueue
+- add Pender, rework Cargo features.
+- add support for turbo-wakers.
+- Allow TaskStorage to auto-implement `Sync`
+- Use AtomicPtr for signal_ctx, removes 1 unsafe.
+- Replace unsound critical sections with atomics
+
+## 0.1.1 - 2022-11-23
+
+- Fix features for documentation
+
+## 0.1.0 - 2022-11-23
+
+- First release