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/esp-metadata/devices/esp32p4.toml

@@ -0,0 +1,98 @@
+[device]
+name  = "esp32p4"
+arch  = "riscv"
+cores = "multi_core"
+
+peripherals = [
+    # Peripherals available in the PAC:
+    # "adc",
+    # "aes",
+    # "assist_debug",
+    # "axi_dma",
+    # "axi_icm",
+    # "bitscrambler",
+    # "cache",
+    # "dma",
+    # "ds",
+    # "ecc",
+    # "ecdsa",
+    "efuse",
+    # "gpio_sd",
+    "gpio",
+    # "h264_dma",
+    # "h264",
+    # "hmac",
+    # "hp_sys_clkrst",
+    "hp_sys",
+    # "i2c0",
+    # "i2c1",
+    # "i2s0",
+    # "i2s1",
+    # "i2s2",
+    # "i3c_mst_mem",
+    # "i3c_mst",
+    # "i3c_slv",
+    "interrupt_core0",
+    "interrupt_core1",
+    "io_mux",
+    # "isp",
+    # "jpeg",
+    # "lcd_cam",
+    # "ledc",
+    # "lp_adc",
+    # "lp_ana_peri",
+    # "lp_aon_clkrst",
+    # "lp_gpio",
+    # "lp_huk",
+    # "lp_i2c_ana_mst",
+    # "lp_i2c0",
+    # "lp_i2s0",
+    # "lp_intr",
+    # "lp_io_mux",
+    # "lp_peri",
+    # "lp_sys",
+    # "lp_timer",
+    # "lp_touch",
+    # "lp_tsens",
+    # "lp_uart",
+    # "lp_wdt",
+    # "mcpwm0",
+    # "mcpwm1",
+    # "mipi_csi_bridge",
+    # "mipi_csi_host",
+    # "mipi_dsi_bridge",
+    # "mipi_dsi_host",
+    # "parl_io",
+    # "pau",
+    # "pcnt",
+    # "pmu",
+    # "ppa",
+    # "pvt",
+    # "rmt",
+    # "rsa",
+    # "sdhost",
+    # "sha",
+    # "soc_etm",
+    # "spi0",
+    # "spi1",
+    # "spi2",
+    # "spi3",
+    # "systimer",
+    # "timg0",
+    # "timg1",
+    # "trace0",
+    # "trace1",
+    # "twai0",
+    # "twai1",
+    # "twai2",
+    # "uart0",
+    # "uhci0",
+    # "usb_device",
+    # "usb_wrap",
+]
+
+symbols = [
+    # Additional peripherals defined by us (the developers):
+    "clic",
+    "very_large_intr_status",
+]