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/futures-util/src/async_await/join_mod.rs

@@ -0,0 +1,110 @@
+//! The `join` macro.
+
+macro_rules! document_join_macro {
+    ($join:item $try_join:item) => {
+        /// Polls multiple futures simultaneously, returning a tuple
+        /// of all results once complete.
+        ///
+        /// While `join!(a, b)` is similar to `(a.await, b.await)`,
+        /// `join!` polls both futures concurrently and therefore is more efficient.
+        ///
+        /// This macro is only usable inside of async functions, closures, and blocks.
+        /// It is also gated behind the `async-await` feature of this library, which is
+        /// activated by default.
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// # futures::executor::block_on(async {
+        /// use futures::join;
+        ///
+        /// let a = async { 1 };
+        /// let b = async { 2 };
+        /// assert_eq!(join!(a, b), (1, 2));
+        ///
+        /// // `join!` is variadic, so you can pass any number of futures
+        /// let c = async { 3 };
+        /// let d = async { 4 };
+        /// let e = async { 5 };
+        /// assert_eq!(join!(c, d, e), (3, 4, 5));
+        /// # });
+        /// ```
+        $join
+
+        /// Polls multiple futures simultaneously, resolving to a [`Result`] containing
+        /// either a tuple of the successful outputs or an error.
+        ///
+        /// `try_join!` is similar to [`join!`], but completes immediately if any of
+        /// the futures return an error.
+        ///
+        /// This macro is only usable inside of async functions, closures, and blocks.
+        /// It is also gated behind the `async-await` feature of this library, which is
+        /// activated by default.
+        ///
+        /// # Examples
+        ///
+        /// When used on multiple futures that return `Ok`, `try_join!` will return
+        /// `Ok` of a tuple of the values:
+        ///
+        /// ```
+        /// # futures::executor::block_on(async {
+        /// use futures::try_join;
+        ///
+        /// let a = async { Ok::<i32, i32>(1) };
+        /// let b = async { Ok::<i32, i32>(2) };
+        /// assert_eq!(try_join!(a, b), Ok((1, 2)));
+        ///
+        /// // `try_join!` is variadic, so you can pass any number of futures
+        /// let c = async { Ok::<i32, i32>(3) };
+        /// let d = async { Ok::<i32, i32>(4) };
+        /// let e = async { Ok::<i32, i32>(5) };
+        /// assert_eq!(try_join!(c, d, e), Ok((3, 4, 5)));
+        /// # });
+        /// ```
+        ///
+        /// If one of the futures resolves to an error, `try_join!` will return
+        /// that error:
+        ///
+        /// ```
+        /// # futures::executor::block_on(async {
+        /// use futures::try_join;
+        ///
+        /// let a = async { Ok::<i32, i32>(1) };
+        /// let b = async { Err::<u64, i32>(2) };
+        ///
+        /// assert_eq!(try_join!(a, b), Err(2));
+        /// # });
+        /// ```
+        $try_join
+    }
+}
+
+#[allow(unreachable_pub)]
+#[doc(hidden)]
+pub use futures_macro::join_internal;
+
+#[allow(unreachable_pub)]
+#[doc(hidden)]
+pub use futures_macro::try_join_internal;
+
+document_join_macro! {
+    #[macro_export]
+    macro_rules! join {
+        ($($tokens:tt)*) => {{
+            use $crate::__private as __futures_crate;
+            $crate::join_internal! {
+                $( $tokens )*
+            }
+        }}
+    }
+
+    #[macro_export]
+    macro_rules! try_join {
+        ($($tokens:tt)*) => {{
+            use $crate::__private as __futures_crate;
+            $crate::try_join_internal! {
+                $( $tokens )*
+            }
+        }}
+    }
+}