feat(03-02): implement animation library — 7 types with registry and factory

- AnimationBase ABC with render(t, led_count) and from_params() contract
- SolidColorAnimation: time-independent uniform fill
- ChaseAnimation: moving lit segment with forward/reverse support
- PulseAnimation: sine-wave breathing effect (speed maps to period)
- RainbowAnimation: HSV hue cycle across strip via colorsys.hsv_to_rgb
- StrobeAnimation: on/off flashing at 1-20 Hz with configurable duty cycle
- ColorWipeAnimation: progressive fill from start or end
- FireAnimation: Fire2012 algorithm with cooling/sparking/heat-to-color mapping
- ANIMATION_REGISTRY + create_animation() factory function
- All 24 tests passing

lightsync/animations/rainbow.py

@@ -0,0 +1,38 @@
+"""Rainbow animation — full HSV hue cycle across the strip."""
+import colorsys
+from lightsync.animations.base import AnimationBase
+
+
+class RainbowAnimation(AnimationBase):
+    """Hue-shifting rainbow across the entire strip.
+
+    period=1.0 means one full rainbow cycle fits on the strip.
+    speed controls how fast the hues shift over time.
+    """
+
+    def __init__(
+        self,
+        speed: float = 0.5,
+        period: float = 1.0,
+    ) -> None:
+        self.speed = speed
+        self.period = period
+
+    def render(self, t: float, led_count: int) -> list[tuple]:
+        pixels = []
+        for i in range(led_count):
+            hue = (i / led_count / self.period + t * self.speed) % 1.0
+            r_f, g_f, b_f = colorsys.hsv_to_rgb(hue, 1.0, 1.0)
+            pixels.append((
+                int(r_f * 255),
+                int(g_f * 255),
+                int(b_f * 255),
+            ))
+        return pixels
+
+    @classmethod
+    def from_params(cls, params: dict) -> "RainbowAnimation":
+        return cls(
+            speed=params.get("speed", 0.5),
+            period=params.get("period", 1.0),
+        )