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/zerocopy/ci/release_crate_version.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+#
+# Copyright 2024 The Fuchsia Authors
+#
+# Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+# <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+# license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+set -e
+
+if [ $# -ne 1 ]; then
+    echo "Usage: $0 <version>" >&2
+    exit 1
+fi
+
+VERSION="$1"
+
+sed -i -e "s/^zerocopy-derive = { version = \"=[0-9a-zA-Z\.-]*\"/zerocopy-derive = { version = \"=$VERSION\"/" Cargo.toml
+sed -i -e "s/^version = \"[0-9a-zA-Z\.-]*\"/version = \"$VERSION\"/" Cargo.toml zerocopy-derive/Cargo.toml
+
+# Ensure that `Cargo.lock` is updated.
+cargo generate-lockfile