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/nvmc_ns.rs

@@ -0,0 +1,52 @@
+#[doc = r"Register block"]
+#[repr(C)]
+pub struct RegisterBlock {
+    _reserved0: [u8; 0x0400],
+    #[doc = "0x400 - Ready flag"]
+    pub ready: READY,
+    _reserved1: [u8; 0x04],
+    #[doc = "0x408 - Ready flag"]
+    pub readynext: READYNEXT,
+    _reserved2: [u8; 0xf8],
+    #[doc = "0x504 - Configuration register"]
+    pub config: CONFIG,
+    _reserved3: [u8; 0x04],
+    #[doc = "0x50c - Register for erasing all non-volatile user memory"]
+    pub eraseall: ERASEALL,
+    _reserved4: [u8; 0x0c],
+    #[doc = "0x51c - Register for partial erase configuration"]
+    pub erasepagepartialcfg: ERASEPAGEPARTIALCFG,
+    _reserved5: [u8; 0x64],
+    #[doc = "0x584 - Non-secure configuration register"]
+    pub configns: CONFIGNS,
+    #[doc = "0x588 - Non-secure APPROTECT enable register"]
+    pub writeuicrns: WRITEUICRNS,
+}
+#[doc = "READY (r) register accessor: an alias for `Reg<READY_SPEC>`"]
+pub type READY = crate::Reg<ready::READY_SPEC>;
+#[doc = "Ready flag"]
+pub mod ready;
+#[doc = "READYNEXT (r) register accessor: an alias for `Reg<READYNEXT_SPEC>`"]
+pub type READYNEXT = crate::Reg<readynext::READYNEXT_SPEC>;
+#[doc = "Ready flag"]
+pub mod readynext;
+#[doc = "CONFIG (rw) register accessor: an alias for `Reg<CONFIG_SPEC>`"]
+pub type CONFIG = crate::Reg<config::CONFIG_SPEC>;
+#[doc = "Configuration register"]
+pub mod config;
+#[doc = "ERASEALL (w) register accessor: an alias for `Reg<ERASEALL_SPEC>`"]
+pub type ERASEALL = crate::Reg<eraseall::ERASEALL_SPEC>;
+#[doc = "Register for erasing all non-volatile user memory"]
+pub mod eraseall;
+#[doc = "ERASEPAGEPARTIALCFG (rw) register accessor: an alias for `Reg<ERASEPAGEPARTIALCFG_SPEC>`"]
+pub type ERASEPAGEPARTIALCFG = crate::Reg<erasepagepartialcfg::ERASEPAGEPARTIALCFG_SPEC>;
+#[doc = "Register for partial erase configuration"]
+pub mod erasepagepartialcfg;
+#[doc = "CONFIGNS (rw) register accessor: an alias for `Reg<CONFIGNS_SPEC>`"]
+pub type CONFIGNS = crate::Reg<configns::CONFIGNS_SPEC>;
+#[doc = "Non-secure configuration register"]
+pub mod configns;
+#[doc = "WRITEUICRNS (w) register accessor: an alias for `Reg<WRITEUICRNS_SPEC>`"]
+pub type WRITEUICRNS = crate::Reg<writeuicrns::WRITEUICRNS_SPEC>;
+#[doc = "Non-secure APPROTECT enable register"]
+pub mod writeuicrns;