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/basic-toml/src/lib.rs

@@ -0,0 +1,144 @@
+//! [![github]](https://github.com/dtolnay/basic-toml) [![crates-io]](https://crates.io/crates/basic-toml) [![docs-rs]](https://docs.rs/basic-toml)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! A library for parsing and producing data in [TOML] format using [Serde].
+//!
+//! TOML is designed to be "a config file format for humans": minimal and easy
+//! to read due to obvious semantics.
+//!
+//! ```toml
+//! [package]
+//! name = "basic-toml"
+#![doc = concat!("version = \"", env!("CARGO_PKG_VERSION_MAJOR"), ".", env!("CARGO_PKG_VERSION_MINOR"), ".", env!("CARGO_PKG_VERSION_PATCH"), "\"")]
+//! authors = ["Alex Crichton <alex@alexcrichton.com>"]
+//!
+//! [dependencies]
+//! serde = "1.0"
+//! ```
+//!
+//! The TOML format is widely used throughout the Rust community for
+//! configuration, notably being used by [Cargo], Rust's package manager.
+//!
+//! [TOML]: https://toml.io
+//! [Serde]: https://serde.rs
+//! [Cargo]: https://crates.io
+//!
+//! # Deserialization
+//!
+//! ```
+//! use semver::{Version, VersionReq};
+//! use serde_derive::Deserialize;
+//! use std::collections::BTreeMap as Map;
+//!
+//! #[derive(Deserialize)]
+//! struct Manifest {
+//!     package: Package,
+//!     #[serde(default)]
+//!     dependencies: Map<String, VersionReq>,
+//! }
+//!
+//! #[derive(Deserialize)]
+//! struct Package {
+//!     name: String,
+//!     version: Version,
+//!     #[serde(default)]
+//!     authors: Vec<String>,
+//! }
+//!
+//! fn main() {
+//!     let manifest: Manifest = basic_toml::from_str(r#"
+//!         [package]
+//!         name = "basic-toml"
+#![doc = concat!("        version = \"", env!("CARGO_PKG_VERSION_MAJOR"), ".", env!("CARGO_PKG_VERSION_MINOR"), ".", env!("CARGO_PKG_VERSION_PATCH"), "\"")]
+//!         authors = ["Alex Crichton <alex@alexcrichton.com>"]
+//!
+//!         [dependencies]
+//!         serde = "^1.0"
+//!     "#).unwrap();
+//!
+//!     assert_eq!(manifest.package.name, "basic-toml");
+#![doc = concat!("    assert_eq!(manifest.package.version, Version::new(", env!("CARGO_PKG_VERSION_MAJOR"), ", ", env!("CARGO_PKG_VERSION_MINOR"), ", ", env!("CARGO_PKG_VERSION_PATCH"), "));")]
+//!     assert_eq!(manifest.package.authors, ["Alex Crichton <alex@alexcrichton.com>"]);
+//!     assert_eq!(manifest.dependencies["serde"].to_string(), "^1.0");
+//! }
+//! ```
+//!
+//! # Serialization
+//!
+//! ```
+//! use semver::{Version, VersionReq};
+//! use serde_derive::Serialize;
+//! use std::collections::BTreeMap as Map;
+//!
+//! #[derive(Serialize)]
+//! struct Manifest {
+//!     package: Package,
+//!     dependencies: Map<String, VersionReq>,
+//! }
+//!
+//! #[derive(Serialize)]
+//! struct Package {
+//!     name: String,
+//!     version: Version,
+//!     authors: Vec<String>,
+//! }
+//!
+//! fn main() {
+//!     let manifest = Manifest {
+//!         package: Package {
+//!             name: "basic-toml".to_owned(),
+#![doc = concat!("            version: Version::new(", env!("CARGO_PKG_VERSION_MAJOR"), ", ", env!("CARGO_PKG_VERSION_MINOR"), ", ", env!("CARGO_PKG_VERSION_PATCH"), "),")]
+//!             authors: vec!["Alex Crichton <alex@alexcrichton.com>".to_owned()],
+//!         },
+//!         dependencies: {
+//!             let mut dependencies = Map::new();
+//!             dependencies.insert("serde".to_owned(), "^1.0".parse().unwrap());
+//!             dependencies
+//!         },
+//!     };
+//!
+//!     let toml = basic_toml::to_string(&manifest).unwrap();
+//!     print!("{}", toml);
+//! }
+//! ```
+//!
+//! # Spec compatibility
+//!
+//! TOML v0.5.0.
+//!
+//! TOML's date and time syntax are not supported.
+
+#![doc(html_root_url = "https://docs.rs/basic-toml/0.1.10")]
+#![deny(missing_docs)]
+#![allow(
+    clippy::bool_to_int_with_if,
+    clippy::elidable_lifetime_names,
+    clippy::let_underscore_untyped,
+    clippy::manual_let_else,
+    clippy::manual_range_contains,
+    clippy::match_like_matches_macro,
+    clippy::missing_errors_doc,
+    clippy::must_use_candidate,
+    clippy::needless_doctest_main,
+    clippy::needless_lifetimes,
+    clippy::needless_pass_by_value,
+    clippy::similar_names,
+    clippy::type_complexity,
+    clippy::uninlined_format_args,
+    clippy::unnecessary_box_returns,
+    clippy::unwrap_or_default
+)]
+
+mod de;
+mod error;
+mod ser;
+mod tokens;
+
+pub use crate::de::{from_slice, from_str};
+pub use crate::error::Error;
+pub use crate::ser::to_string;