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/nrf51-pac/src/temp.rs

@@ -0,0 +1,50 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct RegisterBlock {
+    #[doc = "0x00 - Start temperature measurement."]
+    pub tasks_start: TASKS_START,
+    #[doc = "0x04 - Stop temperature measurement."]
+    pub tasks_stop: TASKS_STOP,
+    _reserved2: [u8; 0xf8],
+    #[doc = "0x100 - Temperature measurement complete, data ready event."]
+    pub events_datardy: EVENTS_DATARDY,
+    _reserved3: [u8; 0x0200],
+    #[doc = "0x304 - Interrupt enable set register."]
+    pub intenset: INTENSET,
+    #[doc = "0x308 - Interrupt enable clear register."]
+    pub intenclr: INTENCLR,
+    _reserved5: [u8; 0x01fc],
+    #[doc = "0x508 - Die temperature in degC, 2's complement format, 0.25 degC pecision."]
+    pub temp: TEMP,
+    _reserved6: [u8; 0x0af0],
+    #[doc = "0xffc - Peripheral power control."]
+    pub power: POWER,
+}
+#[doc = "TASKS_START (w) register accessor: an alias for `Reg<TASKS_START_SPEC>`"]
+pub type TASKS_START = crate::Reg<tasks_start::TASKS_START_SPEC>;
+#[doc = "Start temperature measurement."]
+pub mod tasks_start;
+#[doc = "TASKS_STOP (w) register accessor: an alias for `Reg<TASKS_STOP_SPEC>`"]
+pub type TASKS_STOP = crate::Reg<tasks_stop::TASKS_STOP_SPEC>;
+#[doc = "Stop temperature measurement."]
+pub mod tasks_stop;
+#[doc = "EVENTS_DATARDY (rw) register accessor: an alias for `Reg<EVENTS_DATARDY_SPEC>`"]
+pub type EVENTS_DATARDY = crate::Reg<events_datardy::EVENTS_DATARDY_SPEC>;
+#[doc = "Temperature measurement complete, data ready event."]
+pub mod events_datardy;
+#[doc = "INTENSET (rw) register accessor: an alias for `Reg<INTENSET_SPEC>`"]
+pub type INTENSET = crate::Reg<intenset::INTENSET_SPEC>;
+#[doc = "Interrupt enable set register."]
+pub mod intenset;
+#[doc = "INTENCLR (rw) register accessor: an alias for `Reg<INTENCLR_SPEC>`"]
+pub type INTENCLR = crate::Reg<intenclr::INTENCLR_SPEC>;
+#[doc = "Interrupt enable clear register."]
+pub mod intenclr;
+#[doc = "TEMP (r) register accessor: an alias for `Reg<TEMP_SPEC>`"]
+pub type TEMP = crate::Reg<temp::TEMP_SPEC>;
+#[doc = "Die temperature in degC, 2's complement format, 0.25 degC pecision."]
+pub mod temp;
+#[doc = "POWER (rw) register accessor: an alias for `Reg<POWER_SPEC>`"]
+pub type POWER = crate::Reg<power::POWER_SPEC>;
+#[doc = "Peripheral power control."]
+pub mod power;