feat(patterns): add expanded animation pack with smoke tests

Add a broad set of new pattern modules and matching pattern smoke scripts so the new effects can be validated directly on-device.

src/patterns/snowfall.py

@@ -0,0 +1,36 @@
+import random
+import utime
+
+
+class Snowfall:
+    def __init__(self, driver):
+        self.driver = driver
+
+    def run(self, preset):
+        colors = preset.c if preset.c else [(255, 255, 255), (180, 220, 255)]
+        density = max(1, int(preset.n1) if int(preset.n1) > 0 else 20)
+        speed = max(1, int(preset.n2) if int(preset.n2) > 0 else 1)
+        flakes = []
+        last = utime.ticks_ms()
+        while True:
+            d = max(1, int(preset.d))
+            now = utime.ticks_ms()
+            if utime.ticks_diff(now, last) >= d:
+                if random.randint(0, 255) < density:
+                    flakes.append([self.driver.num_leds - 1, random.randint(0, len(colors)-1)])
+                for i in range(self.driver.num_leds):
+                    self.driver.n[i] = (0, 0, 0)
+                nf = []
+                for pos, ci in flakes:
+                    if 0 <= pos < self.driver.num_leds:
+                        self.driver.n[pos] = self.driver.apply_brightness(colors[ci], preset.b)
+                    pos -= speed
+                    if pos >= -1:
+                        nf.append([pos, ci])
+                flakes = nf
+                self.driver.n.write()
+                last = utime.ticks_add(last, d)
+                if not preset.a:
+                    yield
+                    return
+            yield