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/nrf52810-pac/src/uicr.rs

@@ -0,0 +1,36 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct RegisterBlock {
+    _reserved0: [u8; 0x14],
+    #[doc = "0x14..0x50 - Description collection: Reserved for Nordic firmware design"]
+    pub nrffw: [NRFFW; 15],
+    #[doc = "0x50..0x80 - Description collection: Reserved for Nordic hardware design"]
+    pub nrfhw: [NRFHW; 12],
+    #[doc = "0x80..0x100 - Description collection: Reserved for customer"]
+    pub customer: [CUSTOMER; 32],
+    _reserved3: [u8; 0x0100],
+    #[doc = "0x200..0x208 - Description collection: Mapping of the nRESET function (see POWER chapter for details)"]
+    pub pselreset: [PSELRESET; 2],
+    #[doc = "0x208 - Access port protection"]
+    pub approtect: APPROTECT,
+}
+#[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 = "NRFHW (rw) register accessor: an alias for `Reg<NRFHW_SPEC>`"]
+pub type NRFHW = crate::Reg<nrfhw::NRFHW_SPEC>;
+#[doc = "Description collection: Reserved for Nordic hardware design"]
+pub mod nrfhw;
+#[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;
+#[doc = "PSELRESET (rw) register accessor: an alias for `Reg<PSELRESET_SPEC>`"]
+pub type PSELRESET = crate::Reg<pselreset::PSELRESET_SPEC>;
+#[doc = "Description collection: Mapping of the nRESET function (see POWER chapter for details)"]
+pub mod pselreset;
+#[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;