Replace auto-start with startup automation, add card colors to dashboard

- Add `startup` automation condition type that activates on server boot,
  replacing the per-target `auto_start` flag
- Remove `auto_start` field from targets, scene snapshots, and all API layers
- Remove auto-start UI section and star buttons from dashboard and target cards
- Remove `color` field from scene presets (backend, API, modal, frontend)
- Add card color support to scene preset cards (color picker + border style)
- Show localStorage-backed card colors on all dashboard cards (targets,
  automations, sync clocks, scene presets)
- Fix card color picker updating wrong card when duplicate data attributes
  exist by using closest() from picker wrapper instead of global querySelector
- Add sync clocks step to Sources tab tutorial
- Bump SW cache v9 → v10

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

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

@@ -122,7 +122,6 @@ export function createKCTargetCard(target, sourceMap, patternTemplateMap, valueS
     return wrapCard({
         dataAttr: 'data-kc-target-id',
         id: target.id,
-        topButtons: `<button class="card-autostart-btn${target.auto_start ? ' active' : ''}" onclick="toggleTargetAutoStart('${target.id}', ${!target.auto_start})" title="${target.auto_start ? t('autostart.toggle.enabled') : t('autostart.toggle.disabled')}">&#x2605;</button>`,
         removeOnclick: `deleteKCTarget('${target.id}')`,
         removeTitle: t('common.delete'),
         content: `