feat(01-01): PlatformIO scaffold + config.h

- platformio.ini with -DESP32_ARDUINO_NO_RGB_BUILTIN, NeoPixelBus ^2.8.0, ArduinoJson ^7.4.0
- config.h defines all pin, LED count, brightness, timing, and FreeRTOS constants

firmware/platformio.ini

@@ -0,0 +1,14 @@
+[env:esp32c3_supermini]
+platform = espressif32
+board = esp32-c3-devkitm-1
+framework = arduino
+monitor_speed = 115200
+
+build_flags =
+    -DARDUINO_USB_CDC_ON_BOOT=1
+    -DARDUINO_USB_MODE=1
+    -DESP32_ARDUINO_NO_RGB_BUILTIN
+
+lib_deps =
+    makuna/NeoPixelBus @ ^2.8.0
+    bblanchon/ArduinoJson @ ^7.4.0

firmware/src/config.h

@@ -0,0 +1,49 @@
+#pragma once
+
+// GPIO6/GPIO7 for WS2801 SPI — validate on hardware, fallback: GPIO0/GPIO1 if JTAG conflict
+
+#include <stdint.h>
+#include <freertos/FreeRTOS.h>
+
+// ---------------------------------------------------------------------------
+// Pin assignments (ESP32-C3 SuperMini safe GPIOs)
+// ---------------------------------------------------------------------------
+constexpr uint8_t PIN_SK6812        = 3;    // RMT channel 0, confirmed safe
+constexpr uint8_t PIN_WS2801_MOSI   = 7;    // Hardware SPI MOSI
+constexpr uint8_t PIN_WS2801_CLK    = 6;    // Hardware SPI CLK
+
+// ---------------------------------------------------------------------------
+// LED strip lengths
+// ---------------------------------------------------------------------------
+constexpr uint16_t LED_COUNT_SCHRANK = 160; // WS2801 strip (Schrank, U-turn)
+constexpr uint16_t LED_COUNT_WAND   = 300;  // SK6812 strip (Wand, RGBW)
+
+// ---------------------------------------------------------------------------
+// Brightness limits (per D-09: peak 27A at full brightness, cap at 40%)
+// ---------------------------------------------------------------------------
+constexpr float BRIGHTNESS_CAP      = 0.40f; // 40% hardware max (per D-09)
+constexpr float BRIGHTNESS_MAX      = 0.60f; // 60% user-settable ceiling
+
+// ---------------------------------------------------------------------------
+// Network
+// ---------------------------------------------------------------------------
+constexpr uint16_t UDP_PORT         = 4210;  // Pi-to-ESP command port
+
+// ---------------------------------------------------------------------------
+// Animation engine (per D-04: 50fps tick rate)
+// ---------------------------------------------------------------------------
+constexpr uint8_t ANIM_FPS          = 50;    // 50fps tick rate
+
+// ---------------------------------------------------------------------------
+// FreeRTOS task priorities (higher number = higher priority on single core)
+// ---------------------------------------------------------------------------
+constexpr UBaseType_t PRIORITY_LED_OUTPUT = 3;
+constexpr UBaseType_t PRIORITY_ANIM_TICK  = 2;
+constexpr UBaseType_t PRIORITY_WIFI_RECV  = 1;
+
+// ---------------------------------------------------------------------------
+// FreeRTOS stack sizes (bytes)
+// ---------------------------------------------------------------------------
+constexpr uint32_t STACK_WIFI = 8192;
+constexpr uint32_t STACK_ANIM = 4096;
+constexpr uint32_t STACK_LED  = 2048;