Add color_cycle as standalone source type; UI polish

- color_cycle is now a top-level source type (alongside picture/static/gradient)
  with a configurable color list and cycle_speed; defaults to full rainbow spectrum
- ColorCycleColorStripSource + ColorCycleColorStripStream: smooth 30 fps interpolation
  between user-defined colors, one full cycle every 20s at speed=1.0
- Removed color_cycle animation sub-type from StaticColorStripStream
- Color cycle editor: compact horizontal swatch layout, proper module-scope fix
  (colorCycleAdd/Remove now exposed on window, DOM-synced before mutations)
- Animation enabled + Frame interpolation checkboxes use toggle-switch style
- Removed Potential FPS metric from targets and KC targets metric grids

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

server/src/wled_controller/static/js/features/targets.js

@@ -466,10 +466,6 @@ export function createTargetCard(target, deviceMap, colorStripSourceMap) {
                         <div class="metric-label">${t('device.metrics.target_fps')}</div>
                         <div class="metric-value">${state.fps_target || 0}</div>
                     </div>
-                    <div class="metric">
-                        <div class="metric-label">${t('device.metrics.potential_fps')}</div>
-                        <div class="metric-value">${state.fps_potential?.toFixed(0) || '-'}</div>
-                    </div>
                     <div class="metric">
                         <div class="metric-label">${t('device.metrics.frames')}</div>
                         <div class="metric-value">${metrics.frames_processed || 0}</div>