Remove per-source speed, fix device dirty check, and add frontend caching

Speed is now exclusively controlled via sync clocks — CSS sources no longer
carry their own speed/cycle_speed fields. Streams default to 1.0× when no
clock is assigned. Also fixes false-positive dirty check on the device
settings modal (array reference comparison) and converts several frontend
modules to use DataCache for consistent API response caching.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/api/routes/color_strip_sources.py

@@ -74,9 +74,7 @@ def _css_to_response(source, overlay_active: bool = False) -> ColorStripSourceRe
         color=getattr(source, "color", None),
         stops=stops,
         colors=getattr(source, "colors", None),
-        cycle_speed=getattr(source, "cycle_speed", None),
         effect_type=getattr(source, "effect_type", None),
-        speed=getattr(source, "speed", None),
         palette=getattr(source, "palette", None),
         intensity=getattr(source, "intensity", None),
         scale=getattr(source, "scale", None),
@@ -163,9 +161,7 @@ async def create_color_strip_source(
             frame_interpolation=data.frame_interpolation,
             animation=data.animation.model_dump() if data.animation else None,
             colors=data.colors,
-            cycle_speed=data.cycle_speed,
             effect_type=data.effect_type,
-            speed=data.speed,
             palette=data.palette,
             intensity=data.intensity,
             scale=data.scale,
@@ -241,9 +237,7 @@ async def update_color_strip_source(
             frame_interpolation=data.frame_interpolation,
             animation=data.animation.model_dump() if data.animation else None,
             colors=data.colors,
-            cycle_speed=data.cycle_speed,
             effect_type=data.effect_type,
-            speed=data.speed,
             palette=data.palette,
             intensity=data.intensity,
             scale=data.scale,