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-task/src/lib.rs

@@ -0,0 +1,50 @@
+//! Tools for working with tasks.
+
+#![no_std]
+#![doc(test(
+    no_crate_inject,
+    attr(
+        deny(warnings, rust_2018_idioms, single_use_lifetimes),
+        allow(dead_code, unused_assignments, unused_variables)
+    )
+))]
+#![warn(missing_docs, unsafe_op_in_unsafe_fn)]
+
+#[cfg(feature = "alloc")]
+extern crate alloc;
+#[cfg(feature = "std")]
+extern crate std;
+
+mod spawn;
+pub use crate::spawn::{LocalSpawn, Spawn, SpawnError};
+
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+mod arc_wake;
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+pub use crate::arc_wake::ArcWake;
+
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+mod waker;
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+pub use crate::waker::waker;
+
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+mod waker_ref;
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
+#[cfg(feature = "alloc")]
+pub use crate::waker_ref::{waker_ref, WakerRef};
+
+mod future_obj;
+pub use crate::future_obj::{FutureObj, LocalFutureObj, UnsafeFutureObj};
+
+mod noop_waker;
+pub use crate::noop_waker::noop_waker;
+pub use crate::noop_waker::noop_waker_ref;
+
+#[doc(no_inline)]
+pub use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};