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/pin-project-lite/README.md

@@ -0,0 +1,129 @@
+# pin-project-lite
+
+[![crates.io](https://img.shields.io/crates/v/pin-project-lite?style=flat-square&logo=rust)](https://crates.io/crates/pin-project-lite)
+[![docs.rs](https://img.shields.io/badge/docs.rs-pin--project--lite-blue?style=flat-square&logo=docs.rs)](https://docs.rs/pin-project-lite)
+[![license](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue?style=flat-square)](#license)
+[![msrv](https://img.shields.io/badge/msrv-1.37-blue?style=flat-square&logo=rust)](https://www.rust-lang.org)
+[![github actions](https://img.shields.io/github/actions/workflow/status/taiki-e/pin-project-lite/ci.yml?branch=main&style=flat-square&logo=github)](https://github.com/taiki-e/pin-project-lite/actions)
+
+<!-- tidy:sync-markdown-to-rustdoc:start:src/lib.rs -->
+
+A lightweight version of [pin-project] written with declarative macros.
+
+## Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+pin-project-lite = "0.2"
+```
+
+## Examples
+
+[`pin_project!`] macro creates a projection type covering all the fields of
+struct.
+
+```rust
+use std::pin::Pin;
+
+use pin_project_lite::pin_project;
+
+pin_project! {
+    struct Struct<T, U> {
+        #[pin]
+        pinned: T,
+        unpinned: U,
+    }
+}
+
+impl<T, U> Struct<T, U> {
+    fn method(self: Pin<&mut Self>) {
+        let this = self.project();
+        let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
+        let _: &mut U = this.unpinned; // Normal reference to the field
+    }
+}
+```
+
+To use [`pin_project!`] on enums, you need to name the projection type
+returned from the method.
+
+```rust
+use std::pin::Pin;
+
+use pin_project_lite::pin_project;
+
+pin_project! {
+    #[project = EnumProj]
+    enum Enum<T, U> {
+        Variant { #[pin] pinned: T, unpinned: U },
+    }
+}
+
+impl<T, U> Enum<T, U> {
+    fn method(self: Pin<&mut Self>) {
+        match self.project() {
+            EnumProj::Variant { pinned, unpinned } => {
+                let _: Pin<&mut T> = pinned;
+                let _: &mut U = unpinned;
+            }
+        }
+    }
+}
+```
+
+## [pin-project] vs pin-project-lite
+
+Here are some similarities and differences compared to [pin-project].
+
+### Similar: Safety
+
+pin-project-lite guarantees safety in much the same way as [pin-project].
+Both are completely safe unless you write other unsafe code.
+
+### Different: Minimal design
+
+This library does not tackle as expansive of a range of use cases as
+[pin-project] does. If your use case is not already covered, please use
+[pin-project].
+
+### Different: No proc-macro related dependencies
+
+This is the **only** reason to use this crate. However, **if you already
+have proc-macro related dependencies in your crate's dependency graph, there
+is no benefit from using this crate.** (Note: There is almost no difference
+in the amount of code generated between [pin-project] and pin-project-lite.)
+
+### Different: No useful error messages
+
+This macro does not handle any invalid input. So error messages are not to
+be useful in most cases. If you do need useful error messages, then upon
+error you can pass the same input to [pin-project] to receive a helpful
+description of the compile error.
+
+### Different: No support for custom Unpin implementation
+
+pin-project supports this by [`UnsafeUnpin`][unsafe-unpin]. (`!Unpin` is supported by both [pin-project][not-unpin] and [pin-project-lite][not-unpin-lite].)
+
+### Different: No support for tuple structs and tuple variants
+
+pin-project supports this.
+
+[not-unpin]: https://docs.rs/pin-project/latest/pin_project/attr.pin_project.html#unpin
+[pin-project]: https://github.com/taiki-e/pin-project
+[unsafe-unpin]: https://docs.rs/pin-project/latest/pin_project/attr.pin_project.html#unsafeunpin
+
+<!-- tidy:sync-markdown-to-rustdoc:end -->
+
+[not-unpin-lite]: https://docs.rs/pin-project-lite/latest/pin_project_lite/macro.pin_project.html#unpin
+[`pin_project!`]: https://docs.rs/pin-project-lite/latest/pin_project_lite/macro.pin_project.html
+
+## License
+
+Licensed under either of [Apache License, Version 2.0](LICENSE-APACHE) or
+[MIT license](LICENSE-MIT) at your option.
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.