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-app-pac/src/qspi_ns/xip_enc.rs

@@ -0,0 +1,52 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct XIP_ENC {
+    #[doc = "0x00 - Bits 31:0 of XIP AES KEY"]
+    pub key0: KEY0,
+    #[doc = "0x04 - Bits 63:32 of XIP AES KEY"]
+    pub key1: KEY1,
+    #[doc = "0x08 - Bits 95:64 of XIP AES KEY"]
+    pub key2: KEY2,
+    #[doc = "0x0c - Bits 127:96 of XIP AES KEY"]
+    pub key3: KEY3,
+    #[doc = "0x10 - Bits 31:0 of XIP NONCE"]
+    pub nonce0: NONCE0,
+    #[doc = "0x14 - Bits 63:32 of XIP NONCE"]
+    pub nonce1: NONCE1,
+    #[doc = "0x18 - Bits 95:64 of XIP NONCE"]
+    pub nonce2: NONCE2,
+    #[doc = "0x1c - Enable stream cipher for XIP"]
+    pub enable: ENABLE,
+}
+#[doc = "KEY0 (w) register accessor: an alias for `Reg<KEY0_SPEC>`"]
+pub type KEY0 = crate::Reg<key0::KEY0_SPEC>;
+#[doc = "Bits 31:0 of XIP AES KEY"]
+pub mod key0;
+#[doc = "KEY1 (w) register accessor: an alias for `Reg<KEY1_SPEC>`"]
+pub type KEY1 = crate::Reg<key1::KEY1_SPEC>;
+#[doc = "Bits 63:32 of XIP AES KEY"]
+pub mod key1;
+#[doc = "KEY2 (w) register accessor: an alias for `Reg<KEY2_SPEC>`"]
+pub type KEY2 = crate::Reg<key2::KEY2_SPEC>;
+#[doc = "Bits 95:64 of XIP AES KEY"]
+pub mod key2;
+#[doc = "KEY3 (w) register accessor: an alias for `Reg<KEY3_SPEC>`"]
+pub type KEY3 = crate::Reg<key3::KEY3_SPEC>;
+#[doc = "Bits 127:96 of XIP AES KEY"]
+pub mod key3;
+#[doc = "NONCE0 (w) register accessor: an alias for `Reg<NONCE0_SPEC>`"]
+pub type NONCE0 = crate::Reg<nonce0::NONCE0_SPEC>;
+#[doc = "Bits 31:0 of XIP NONCE"]
+pub mod nonce0;
+#[doc = "NONCE1 (w) register accessor: an alias for `Reg<NONCE1_SPEC>`"]
+pub type NONCE1 = crate::Reg<nonce1::NONCE1_SPEC>;
+#[doc = "Bits 63:32 of XIP NONCE"]
+pub mod nonce1;
+#[doc = "NONCE2 (w) register accessor: an alias for `Reg<NONCE2_SPEC>`"]
+pub type NONCE2 = crate::Reg<nonce2::NONCE2_SPEC>;
+#[doc = "Bits 95:64 of XIP NONCE"]
+pub mod nonce2;
+#[doc = "ENABLE (rw) register accessor: an alias for `Reg<ENABLE_SPEC>`"]
+pub type ENABLE = crate::Reg<enable::ENABLE_SPEC>;
+#[doc = "Enable stream cipher for XIP"]
+pub mod enable;