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/tests/expand/default/struct.expanded.rs

@@ -0,0 +1,107 @@
+use pin_project_lite::pin_project;
+struct Struct<T, U> {
+    pinned: T,
+    unpinned: U,
+}
+#[allow(
+    explicit_outlives_requirements,
+    single_use_lifetimes,
+    clippy::unknown_clippy_lints,
+    clippy::absolute_paths,
+    clippy::min_ident_chars,
+    clippy::redundant_pub_crate,
+    clippy::single_char_lifetime_names,
+    clippy::used_underscore_binding
+)]
+const _: () = {
+    #[doc(hidden)]
+    #[allow(
+        dead_code,
+        single_use_lifetimes,
+        clippy::unknown_clippy_lints,
+        clippy::absolute_paths,
+        clippy::min_ident_chars,
+        clippy::mut_mut,
+        clippy::redundant_pub_crate,
+        clippy::ref_option_ref,
+        clippy::single_char_lifetime_names,
+        clippy::type_repetition_in_bounds
+    )]
+    struct Projection<'__pin, T, U>
+    where
+        Struct<T, U>: '__pin,
+    {
+        pinned: ::pin_project_lite::__private::Pin<&'__pin mut (T)>,
+        unpinned: &'__pin mut (U),
+    }
+    #[doc(hidden)]
+    #[allow(
+        dead_code,
+        single_use_lifetimes,
+        clippy::unknown_clippy_lints,
+        clippy::absolute_paths,
+        clippy::min_ident_chars,
+        clippy::mut_mut,
+        clippy::redundant_pub_crate,
+        clippy::ref_option_ref,
+        clippy::single_char_lifetime_names,
+        clippy::type_repetition_in_bounds
+    )]
+    struct ProjectionRef<'__pin, T, U>
+    where
+        Struct<T, U>: '__pin,
+    {
+        pinned: ::pin_project_lite::__private::Pin<&'__pin (T)>,
+        unpinned: &'__pin (U),
+    }
+    impl<T, U> Struct<T, U> {
+        #[doc(hidden)]
+        #[inline]
+        fn project<'__pin>(
+            self: ::pin_project_lite::__private::Pin<&'__pin mut Self>,
+        ) -> Projection<'__pin, T, U> {
+            unsafe {
+                let Self { pinned, unpinned } = self.get_unchecked_mut();
+                Projection {
+                    pinned: ::pin_project_lite::__private::Pin::new_unchecked(pinned),
+                    unpinned: unpinned,
+                }
+            }
+        }
+        #[doc(hidden)]
+        #[inline]
+        fn project_ref<'__pin>(
+            self: ::pin_project_lite::__private::Pin<&'__pin Self>,
+        ) -> ProjectionRef<'__pin, T, U> {
+            unsafe {
+                let Self { pinned, unpinned } = self.get_ref();
+                ProjectionRef {
+                    pinned: ::pin_project_lite::__private::Pin::new_unchecked(pinned),
+                    unpinned: unpinned,
+                }
+            }
+        }
+    }
+    #[allow(non_snake_case)]
+    struct __Origin<'__pin, T, U> {
+        __dummy_lifetime: ::pin_project_lite::__private::PhantomData<&'__pin ()>,
+        pinned: T,
+        unpinned: ::pin_project_lite::__private::AlwaysUnpin<U>,
+    }
+    impl<'__pin, T, U> ::pin_project_lite::__private::Unpin for Struct<T, U>
+    where
+        ::pin_project_lite::__private::PinnedFieldsOf<
+            __Origin<'__pin, T, U>,
+        >: ::pin_project_lite::__private::Unpin,
+    {}
+    trait MustNotImplDrop {}
+    #[allow(clippy::drop_bounds, drop_bounds)]
+    impl<T: ::pin_project_lite::__private::Drop> MustNotImplDrop for T {}
+    impl<T, U> MustNotImplDrop for Struct<T, U> {}
+    #[forbid(unaligned_references, safe_packed_borrows)]
+    fn __assert_not_repr_packed<T, U>(this: &Struct<T, U>) {
+        let _ = &this.pinned;
+        let _ = &this.unpinned;
+    }
+};
+fn main() {}