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/ui/pinned_drop/call-drop-inner.rs

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use pin_project_lite::pin_project;
+
+pin_project! {
+    pub struct S {
+        #[pin]
+        field: u8,
+    }
+    impl PinnedDrop for S {
+        fn drop(this: Pin<&mut Self>) {
+            __drop_inner(this);
+        }
+    }
+}
+
+fn main() {
+    let _x = S { field: 0 };
+}

vendor/pin-project-lite/tests/ui/pinned_drop/call-drop-inner.stderr

@@ -0,0 +1,22 @@
+error[E0061]: this function takes 0 arguments but 1 argument was supplied
+  --> tests/ui/pinned_drop/call-drop-inner.rs:12:13
+   |
+12 |             __drop_inner(this);
+   |             ^^^^^^^^^^^^ ---- unexpected argument of type `Pin<&mut S>`
+   |
+note: function defined here
+  --> tests/ui/pinned_drop/call-drop-inner.rs:5:1
+   |
+ 5 | / pin_project! {
+ 6 | |     pub struct S {
+ 7 | |         #[pin]
+ 8 | |         field: u8,
+...  |
+15 | | }
+   | |_^
+   = note: this error originates in the macro `$crate::__pin_project_make_drop_impl` which comes from the expansion of the macro `pin_project` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: remove the extra argument
+   |
+12 -             __drop_inner(this);
+12 +             __drop_inner();
+   |

vendor/pin-project-lite/tests/ui/pinned_drop/conditional-drop-impl.rs

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use pin_project_lite::pin_project;
+
+// In `Drop` impl, the implementor must specify the same requirement as type definition.
+
+struct DropImpl<T> {
+    f: T,
+}
+
+impl<T: Unpin> Drop for DropImpl<T> {
+    //~^ ERROR E0367
+    fn drop(&mut self) {}
+}
+
+pin_project! {
+    //~^ ERROR E0367
+    struct PinnedDropImpl<T> {
+        #[pin]
+        f: T,
+    }
+
+    impl<T: Unpin> PinnedDrop for PinnedDropImpl<T> {
+        fn drop(_this: Pin<&mut Self>) {}
+    }
+}
+
+fn main() {}

vendor/pin-project-lite/tests/ui/pinned_drop/conditional-drop-impl.stderr

@@ -0,0 +1,34 @@
+error[E0367]: `Drop` impl requires `T: Unpin` but the struct it is implemented for does not
+  --> tests/ui/pinned_drop/conditional-drop-impl.rs:11:9
+   |
+11 | impl<T: Unpin> Drop for DropImpl<T> {
+   |         ^^^^^
+   |
+note: the implementor must specify the same requirement
+  --> tests/ui/pinned_drop/conditional-drop-impl.rs:7:1
+   |
+ 7 | struct DropImpl<T> {
+   | ^^^^^^^^^^^^^^^^^^
+
+error[E0367]: `Drop` impl requires `T: Unpin` but the struct it is implemented for does not
+  --> tests/ui/pinned_drop/conditional-drop-impl.rs:16:1
+   |
+16 | / pin_project! {
+17 | |     //~^ ERROR E0367
+18 | |     struct PinnedDropImpl<T> {
+19 | |         #[pin]
+...  |
+26 | | }
+   | |_^
+   |
+note: the implementor must specify the same requirement
+  --> tests/ui/pinned_drop/conditional-drop-impl.rs:16:1
+   |
+16 | / pin_project! {
+17 | |     //~^ ERROR E0367
+18 | |     struct PinnedDropImpl<T> {
+19 | |         #[pin]
+...  |
+26 | | }
+   | |_^
+   = note: this error originates in the macro `$crate::__pin_project_make_drop_impl` which comes from the expansion of the macro `pin_project` (in Nightly builds, run with -Z macro-backtrace for more info)