feat(01-01): create package structure, Pydantic models, and device abstractions

- pyproject.toml with FastAPI, uvicorn, Pydantic v2, aiofiles, structlog deps
- DeviceConfig Pydantic model with StripType, UUID, validation constraints
- ShowModel with AudioRef, TrackModel, CueModel, AnalysisBlock, schema_version=1
- BaseDevice ABC with encode_frame, encode_animation_cmd, bytes_per_pixel
- SK6812Device (4 bytes/pixel) and WS2801Device (3 bytes/pixel) implementations

lightsync/devices/sk6812.py

@@ -0,0 +1,28 @@
+from lightsync.devices.base import BaseDevice
+from lightsync.models.device import DeviceConfig
+
+
+class SK6812Device(BaseDevice):
+    """SK6812 RGBW LED strip — 4 bytes per pixel (R, G, B, W)."""
+
+    def __init__(self, config: DeviceConfig):
+        super().__init__(config)
+
+    @property
+    def bytes_per_pixel(self) -> int:
+        return 4
+
+    def encode_frame(self, pixels: list[tuple]) -> bytes:
+        """Encode pixel list to SK6812 frame bytes.
+        Each pixel: (r, g, b, w) tuple — 4 bytes per LED.
+        """
+        buf = bytearray()
+        for pixel in pixels:
+            r, g, b = pixel[0], pixel[1], pixel[2]
+            w = pixel[3] if len(pixel) > 3 else 0
+            buf.extend([r & 0xFF, g & 0xFF, b & 0xFF, w & 0xFF])
+        return bytes(buf)
+
+    def encode_animation_cmd(self, animation: str, params: dict) -> bytes:
+        """Stub — Phase 3 implements real animation command encoding."""
+        return b""