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/nrf52805-pac/src/ficr.rs

@@ -0,0 +1,65 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct RegisterBlock {
+    _reserved0: [u8; 0x10],
+    #[doc = "0x10 - Code memory page size"]
+    pub codepagesize: CODEPAGESIZE,
+    #[doc = "0x14 - Code memory size"]
+    pub codesize: CODESIZE,
+    _reserved2: [u8; 0x48],
+    #[doc = "0x60..0x68 - Description collection: Device identifier"]
+    pub deviceid: [DEVICEID; 2],
+    _reserved3: [u8; 0x18],
+    #[doc = "0x80..0x90 - Description collection: Encryption root, word n"]
+    pub er: [ER; 4],
+    #[doc = "0x90..0xa0 - Description collection: Identity root, word n"]
+    pub ir: [IR; 4],
+    #[doc = "0xa0 - Device address type"]
+    pub deviceaddrtype: DEVICEADDRTYPE,
+    #[doc = "0xa4..0xac - Description collection: Device address n"]
+    pub deviceaddr: [DEVICEADDR; 2],
+    _reserved7: [u8; 0x54],
+    #[doc = "0x100..0x114 - Device info"]
+    pub info: INFO,
+    _reserved8: [u8; 0x02f0],
+    #[doc = "0x404..0x448 - Registers storing factory TEMP module linearization coefficients"]
+    pub temp: TEMP,
+}
+#[doc = "CODEPAGESIZE (r) register accessor: an alias for `Reg<CODEPAGESIZE_SPEC>`"]
+pub type CODEPAGESIZE = crate::Reg<codepagesize::CODEPAGESIZE_SPEC>;
+#[doc = "Code memory page size"]
+pub mod codepagesize;
+#[doc = "CODESIZE (r) register accessor: an alias for `Reg<CODESIZE_SPEC>`"]
+pub type CODESIZE = crate::Reg<codesize::CODESIZE_SPEC>;
+#[doc = "Code memory size"]
+pub mod codesize;
+#[doc = "DEVICEID (r) register accessor: an alias for `Reg<DEVICEID_SPEC>`"]
+pub type DEVICEID = crate::Reg<deviceid::DEVICEID_SPEC>;
+#[doc = "Description collection: Device identifier"]
+pub mod deviceid;
+#[doc = "ER (r) register accessor: an alias for `Reg<ER_SPEC>`"]
+pub type ER = crate::Reg<er::ER_SPEC>;
+#[doc = "Description collection: Encryption root, word n"]
+pub mod er;
+#[doc = "IR (r) register accessor: an alias for `Reg<IR_SPEC>`"]
+pub type IR = crate::Reg<ir::IR_SPEC>;
+#[doc = "Description collection: Identity root, word n"]
+pub mod ir;
+#[doc = "DEVICEADDRTYPE (r) register accessor: an alias for `Reg<DEVICEADDRTYPE_SPEC>`"]
+pub type DEVICEADDRTYPE = crate::Reg<deviceaddrtype::DEVICEADDRTYPE_SPEC>;
+#[doc = "Device address type"]
+pub mod deviceaddrtype;
+#[doc = "DEVICEADDR (r) register accessor: an alias for `Reg<DEVICEADDR_SPEC>`"]
+pub type DEVICEADDR = crate::Reg<deviceaddr::DEVICEADDR_SPEC>;
+#[doc = "Description collection: Device address n"]
+pub mod deviceaddr;
+#[doc = "Device info"]
+pub use info::INFO;
+#[doc = r"Cluster"]
+#[doc = "Device info"]
+pub mod info;
+#[doc = "Registers storing factory TEMP module linearization coefficients"]
+pub use temp::TEMP;
+#[doc = r"Cluster"]
+#[doc = "Registers storing factory TEMP module linearization coefficients"]
+pub mod temp;