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/include/basic.rs

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// default pin_project! is completely safe.
+
+::pin_project_lite::pin_project! {
+    /// Testing default struct.
+    #[derive(Debug)]
+    #[allow(clippy::exhaustive_structs)] // for the type itself
+    pub struct DefaultStruct<T, U> {
+        #[pin]
+        pub pinned: T,
+        pub unpinned: U,
+    }
+}
+
+::pin_project_lite::pin_project! {
+    /// Testing named struct.
+    #[allow(clippy::exhaustive_structs)] // for the type itself
+    #[project = DefaultStructProj]
+    #[project_ref = DefaultStructProjRef]
+    #[derive(Debug)]
+    pub struct DefaultStructNamed<T, U> {
+        #[pin]
+        pub pinned: T,
+        pub unpinned: U,
+    }
+}
+
+::pin_project_lite::pin_project! {
+    /// Testing enum.
+    #[allow(clippy::exhaustive_enums)] // for the type itself
+    #[project = DefaultEnumProj]
+    #[project_ref = DefaultEnumProjRef]
+    #[derive(Debug)]
+    pub enum DefaultEnum<T, U> {
+        /// Struct variant.
+        Struct {
+            #[pin]
+            pinned: T,
+            unpinned: U,
+        },
+        /// Unit variant.
+        Unit,
+    }
+}
+
+::pin_project_lite::pin_project! {
+    /// Testing pinned drop struct.
+    #[allow(clippy::exhaustive_structs)] // for the type itself
+    #[derive(Debug)]
+    pub struct PinnedDropStruct<T, U> {
+        #[pin]
+        pub pinned: T,
+        pub unpinned: U,
+    }
+    impl<T, U> PinnedDrop for PinnedDropStruct<T, U> {
+        fn drop(_this: Pin<&mut Self>) {}
+    }
+}
+
+::pin_project_lite::pin_project! {
+    /// Testing pinned drop enum.
+    #[allow(clippy::absolute_paths, clippy::exhaustive_enums)] // for the type itself
+    #[project = PinnedDropEnumProj]
+    #[project_ref = PinnedDropEnumProjRef]
+    #[derive(Debug)]
+    pub enum PinnedDropEnum<T: ::pin_project_lite::__private::Unpin, U> {
+        /// Struct variant.
+        Struct {
+            #[pin]
+            pinned: T,
+            unpinned: U,
+        },
+        /// Unit variant.
+        Unit,
+    }
+    #[allow(clippy::absolute_paths)]
+    impl<T: ::pin_project_lite::__private::Unpin, U> PinnedDrop for PinnedDropEnum<T, U> {
+        fn drop(_this: Pin<&mut Self>) {}
+    }
+}