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/naming/enum-mut.expanded.rs

@@ -0,0 +1,76 @@
+use pin_project_lite::pin_project;
+enum Enum<T, U> {
+    Struct { pinned: T, unpinned: U },
+    Unit,
+}
+#[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
+)]
+enum EnumProj<'__pin, T, U>
+where
+    Enum<T, U>: '__pin,
+{
+    Struct {
+        pinned: ::pin_project_lite::__private::Pin<&'__pin mut (T)>,
+        unpinned: &'__pin mut (U),
+    },
+    Unit,
+}
+#[allow(
+    single_use_lifetimes,
+    clippy::unknown_clippy_lints,
+    clippy::absolute_paths,
+    clippy::min_ident_chars,
+    clippy::single_char_lifetime_names,
+    clippy::used_underscore_binding
+)]
+const _: () = {
+    impl<T, U> Enum<T, U> {
+        #[doc(hidden)]
+        #[inline]
+        fn project<'__pin>(
+            self: ::pin_project_lite::__private::Pin<&'__pin mut Self>,
+        ) -> EnumProj<'__pin, T, U> {
+            unsafe {
+                match self.get_unchecked_mut() {
+                    Self::Struct { pinned, unpinned } => {
+                        EnumProj::Struct {
+                            pinned: ::pin_project_lite::__private::Pin::new_unchecked(
+                                pinned,
+                            ),
+                            unpinned: unpinned,
+                        }
+                    }
+                    Self::Unit => EnumProj::Unit,
+                }
+            }
+        }
+    }
+    #[allow(non_snake_case)]
+    struct __Origin<'__pin, T, U> {
+        __dummy_lifetime: ::pin_project_lite::__private::PhantomData<&'__pin ()>,
+        Struct: (T, ::pin_project_lite::__private::AlwaysUnpin<U>),
+        Unit: (),
+    }
+    impl<'__pin, T, U> ::pin_project_lite::__private::Unpin for Enum<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 Enum<T, U> {}
+};
+fn main() {}