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/uicr_ns.rs

@@ -0,0 +1,30 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct RegisterBlock {
+    #[doc = "0x00 - Access port protection"]
+    pub approtect: APPROTECT,
+    #[doc = "0x04 - Erase protection"]
+    pub eraseprotect: ERASEPROTECT,
+    _reserved2: [u8; 0x01f8],
+    #[doc = "0x200..0x280 - Description collection: Reserved for Nordic firmware design"]
+    pub nrffw: [NRFFW; 32],
+    _reserved3: [u8; 0x80],
+    #[doc = "0x300..0x380 - Description collection: Reserved for customer"]
+    pub customer: [CUSTOMER; 32],
+}
+#[doc = "APPROTECT (rw) register accessor: an alias for `Reg<APPROTECT_SPEC>`"]
+pub type APPROTECT = crate::Reg<approtect::APPROTECT_SPEC>;
+#[doc = "Access port protection"]
+pub mod approtect;
+#[doc = "ERASEPROTECT (rw) register accessor: an alias for `Reg<ERASEPROTECT_SPEC>`"]
+pub type ERASEPROTECT = crate::Reg<eraseprotect::ERASEPROTECT_SPEC>;
+#[doc = "Erase protection"]
+pub mod eraseprotect;
+#[doc = "NRFFW (rw) register accessor: an alias for `Reg<NRFFW_SPEC>`"]
+pub type NRFFW = crate::Reg<nrffw::NRFFW_SPEC>;
+#[doc = "Description collection: Reserved for Nordic firmware design"]
+pub mod nrffw;
+#[doc = "CUSTOMER (rw) register accessor: an alias for `Reg<CUSTOMER_SPEC>`"]
+pub type CUSTOMER = crate::Reg<customer::CUSTOMER_SPEC>;
+#[doc = "Description collection: Reserved for customer"]
+pub mod customer;