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/nrf5340-net-pac/src/ctrlap_ns/eraseprotect.rs

@@ -0,0 +1,16 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct ERASEPROTECT {
+    #[doc = "0x00 - This register locks the ERASEPROTECT.DISABLE register from being written until next reset."]
+    pub lock: LOCK,
+    #[doc = "0x04 - This register disables the ERASEPROTECT register and performs an ERASEALL operation."]
+    pub disable: DISABLE,
+}
+#[doc = "LOCK (rw) register accessor: an alias for `Reg<LOCK_SPEC>`"]
+pub type LOCK = crate::Reg<lock::LOCK_SPEC>;
+#[doc = "This register locks the ERASEPROTECT.DISABLE register from being written until next reset."]
+pub mod lock;
+#[doc = "DISABLE (rw) register accessor: an alias for `Reg<DISABLE_SPEC>`"]
+pub type DISABLE = crate::Reg<disable::DISABLE_SPEC>;
+#[doc = "This register disables the ERASEPROTECT register and performs an ERASEALL operation."]
+pub mod disable;