Add multi-panel Pico UDP firmware and Python LED control.

Pico panels get static IPs on 10.1.1.10–14 with per-panel LED counts, Makefile deploy targets, and Python examples for animations, sync tests, and direct Pi SPI control.

Co-authored-by: Cursor <cursoragent@cursor.com>

leds/backends/spi.py

@@ -0,0 +1,81 @@
+"""WS2812 over SPI — works on Pi 5, 4, and Zero when SPI is enabled."""
+
+from __future__ import annotations
+
+from array import array
+
+try:
+    from spidev import SpiDev
+except ImportError as exc:  # pragma: no cover - import guard
+    SpiDev = None
+    _SPI_IMPORT_ERROR = exc
+else:
+    _SPI_IMPORT_ERROR = None
+
+# WS2812 bit patterns via SPI, from https://github.com/mattaw/ws2812_spi_python
+_LED_ZERO = 0b1100_0000
+_LED_ONE = 0b1111_1100
+_PREAMBLE = 42
+
+
+class SpiBackend:
+    def __init__(
+        self,
+        led_count: int,
+        *,
+        spi_bus: int = 0,
+        spi_device: int = 0,
+        max_speed_hz: int = 6_500_000,
+    ) -> None:
+        if SpiDev is None:
+            raise ImportError(
+                "spidev is required for the SPI backend; install portal requirements"
+            ) from _SPI_IMPORT_ERROR
+
+        self._led_count = led_count
+        self._device = SpiDev()
+        self._device.open(spi_bus, spi_device)
+        self._device.max_speed_hz = max_speed_hz
+        self._device.mode = 0b00
+        self._device.lsbfirst = False
+
+        frame_len = _PREAMBLE + led_count * 24
+        self._frame = array("B", [0] * frame_len)
+        self._clear_frame = array("B", [0] * frame_len)
+        for i in range(_PREAMBLE, frame_len):
+            self._clear_frame[i] = _LED_ZERO
+
+    @property
+    def led_count(self) -> int:
+        return self._led_count
+
+    def write_grb(self, grb_bytes: bytes) -> None:
+        if len(grb_bytes) != self._led_count * 3:
+            raise ValueError(
+                f"expected {self._led_count * 3} bytes, got {len(grb_bytes)}"
+            )
+
+        out = self._frame
+        pos = _PREAMBLE
+        for value in grb_bytes:
+            for bit in (128, 64, 32, 16, 8, 4, 2, 1):
+                out[pos] = _LED_ONE if value & bit else _LED_ZERO
+                pos += 1
+
+        # writebytes2 handles large frames (400+ LEDs); writebytes is capped at 4 KiB.
+        self._device.writebytes2(out)
+
+    def clear(self) -> None:
+        self._device.writebytes2(self._clear_frame)
+
+    def close(self) -> None:
+        try:
+            self.clear()
+        finally:
+            self._device.close()
+
+    def __enter__(self) -> SpiBackend:
+        return self
+
+    def __exit__(self, *_exc) -> None:
+        self.close()