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/future/mod.rs

@@ -0,0 +1,134 @@
+//! Asynchronous values.
+//!
+//! This module contains:
+//!
+//! - The [`Future`] trait.
+//! - The [`FutureExt`] and [`TryFutureExt`] trait, which provides adapters for
+//!   chaining and composing futures.
+//! - Top-level future combinators like [`lazy`](lazy()) which creates a future
+//!   from a closure that defines its return value, and [`ready`](ready()),
+//!   which constructs a future with an immediate defined value.
+
+#[doc(no_inline)]
+pub use core::future::Future;
+
+#[cfg(feature = "alloc")]
+pub use futures_core::future::{BoxFuture, LocalBoxFuture};
+pub use futures_core::future::{FusedFuture, TryFuture};
+pub use futures_task::{FutureObj, LocalFutureObj, UnsafeFutureObj};
+
+// Extension traits and combinators
+#[allow(clippy::module_inception)]
+mod future;
+pub use self::future::{
+    Flatten, Fuse, FutureExt, Inspect, IntoStream, Map, MapInto, NeverError, Then, UnitError,
+};
+
+#[deprecated(note = "This is now an alias for [Flatten](Flatten)")]
+pub use self::future::FlattenStream;
+
+#[cfg(feature = "std")]
+pub use self::future::CatchUnwind;
+
+#[cfg(feature = "channel")]
+#[cfg_attr(docsrs, doc(cfg(feature = "channel")))]
+#[cfg(feature = "std")]
+pub use self::future::{Remote, RemoteHandle};
+
+#[cfg(any(feature = "std", all(feature = "alloc", feature = "spin")))]
+pub use self::future::{Shared, WeakShared};
+
+mod try_future;
+pub use self::try_future::{
+    AndThen, ErrInto, InspectErr, InspectOk, IntoFuture, MapErr, MapOk, MapOkOrElse, OkInto,
+    OrElse, TryFlatten, TryFlattenStream, TryFutureExt, UnwrapOrElse,
+};
+
+#[cfg(feature = "sink")]
+#[cfg_attr(docsrs, doc(cfg(feature = "sink")))]
+pub use self::try_future::FlattenSink;
+
+// Primitive futures
+
+mod lazy;
+pub use self::lazy::{lazy, Lazy};
+
+mod pending;
+pub use self::pending::{pending, Pending};
+
+mod maybe_done;
+pub use self::maybe_done::{maybe_done, MaybeDone};
+
+mod try_maybe_done;
+pub use self::try_maybe_done::{try_maybe_done, TryMaybeDone};
+
+mod option;
+pub use self::option::OptionFuture;
+
+mod poll_fn;
+pub use self::poll_fn::{poll_fn, PollFn};
+
+mod poll_immediate;
+pub use self::poll_immediate::{poll_immediate, PollImmediate};
+
+mod ready;
+pub use self::ready::{err, ok, ready, Ready};
+
+mod always_ready;
+pub use self::always_ready::{always_ready, AlwaysReady};
+
+mod join;
+pub use self::join::{join, join3, join4, join5, Join, Join3, Join4, Join5};
+
+#[cfg(feature = "alloc")]
+mod join_all;
+#[cfg(feature = "alloc")]
+pub use self::join_all::{join_all, JoinAll};
+
+mod select;
+pub use self::select::{select, Select};
+
+#[cfg(feature = "alloc")]
+mod select_all;
+#[cfg(feature = "alloc")]
+pub use self::select_all::{select_all, SelectAll};
+
+mod try_join;
+pub use self::try_join::{
+    try_join, try_join3, try_join4, try_join5, TryJoin, TryJoin3, TryJoin4, TryJoin5,
+};
+
+#[cfg(feature = "alloc")]
+mod try_join_all;
+#[cfg(feature = "alloc")]
+pub use self::try_join_all::{try_join_all, TryJoinAll};
+
+mod try_select;
+pub use self::try_select::{try_select, TrySelect};
+
+#[cfg(feature = "alloc")]
+mod select_ok;
+#[cfg(feature = "alloc")]
+pub use self::select_ok::{select_ok, SelectOk};
+
+mod either;
+pub use self::either::Either;
+
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+mod abortable;
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+pub use crate::abortable::{AbortHandle, AbortRegistration, Abortable, Aborted};
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+pub use abortable::abortable;
+
+// Just a helper function to ensure the futures we're returning all have the
+// right implementations.
+pub(crate) fn assert_future<T, F>(future: F) -> F
+where
+    F: Future<Output = T>,
+{
+    future
+}