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/benches/try_read_from_bytes.x86-64

@@ -0,0 +1,23 @@
+bench_try_read_from_bytes_static_size:
+	mov ax, -16191
+	cmp rsi, 6
+	jne .LBB5_1
+	mov ecx, dword ptr [rdi]
+	movzx edx, cx
+	cmp edx, 49344
+	jne .LBB5_4
+	movzx eax, word ptr [rdi + 4]
+	shl rax, 32
+	or rcx, rax
+	shr rcx, 16
+	mov ax, -16192
+.LBB5_4:
+	shl rcx, 16
+	movzx eax, ax
+	or rax, rcx
+	ret
+.LBB5_1:
+	shl rcx, 16
+	movzx eax, ax
+	or rax, rcx
+	ret