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/pin_project/conflict-unpin.rs

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use pin_project_lite::pin_project;
+
+// The same implementation.
+
+pin_project! { //~ ERROR E0119
+    struct Foo<T, U> {
+        #[pin]
+        future: T,
+        field: U,
+    }
+}
+
+// conflicting implementations
+impl<T, U> Unpin for Foo<T, U> where T: Unpin {} // Conditional Unpin impl
+
+// The implementation that under different conditions.
+
+pin_project! { //~ ERROR E0119
+    struct Bar<T, U> {
+        #[pin]
+        future: T,
+        field: U,
+    }
+}
+
+// conflicting implementations
+impl<T, U> Unpin for Bar<T, U> {} // Non-conditional Unpin impl
+
+pin_project! { //~ ERROR E0119
+    struct Baz<T, U> {
+        #[pin]
+        future: T,
+        field: U,
+    }
+}
+
+// conflicting implementations
+impl<T: Unpin, U: Unpin> Unpin for Baz<T, U> {} // Conditional Unpin impl
+
+pin_project! { //~ ERROR E0119
+    #[project(!Unpin)]
+    struct Qux<T, U> {
+        #[pin]
+        future: T,
+        field: U,
+    }
+}
+
+// conflicting implementations
+impl<T, U> Unpin for Qux<T, U> {} // Non-conditional Unpin impl
+
+pin_project! { //~ ERROR E0119
+    #[project(!Unpin)]
+    struct Fred<T, U> {
+        #[pin]
+        future: T,
+        field: U,
+    }
+}
+
+// conflicting implementations
+impl<T: Unpin, U: Unpin> Unpin for Fred<T, U> {} // Conditional Unpin impl
+
+fn main() {}