fix(patterns): use preset background fallback across animations

Align pattern background rendering to use preset.background_or(...) and update pulse/radiate single-step behaviour to preserve visible frames and step progression.

src/main.py

@@ -173,13 +173,6 @@ async def presets_loop():
     while True:
         presets.tick()
         wdt.feed()
-        if bool(getattr(presets, "debug", False)):
-            now = utime.ticks_ms()
-            if utime.ticks_diff(now, last_mem_log) >= 5000:
-                gc.collect()
-                print("mem runtime:", {"free": gc.mem_free(), "alloc": gc.mem_alloc()})
-                last_mem_log = now
-        # tick() does not await; yield so UDP hello and HTTP/WebSocket can run.
         await asyncio.sleep(0)