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/templates/modals/scene-preset-editor.html

@@ -27,15 +27,6 @@
                     <input type="text" id="scene-preset-editor-description">
                 </div>
 
-                <div class="form-group">
-                    <div class="label-row">
-                        <label for="scene-preset-editor-color" data-i18n="scenes.color">Card Color:</label>
-                        <button type="button" class="hint-toggle" onclick="toggleHint(this)" title="?">?</button>
-                    </div>
-                    <small class="input-hint" style="display:none" data-i18n="scenes.color.hint">Accent color for the scene card on the dashboard</small>
-                    <input type="color" id="scene-preset-editor-color" value="#4fc3f7">
-                </div>
-
                 <div class="form-group" id="scene-target-selector-group" style="display:none">
                     <div class="label-row">
                         <label data-i18n="scenes.targets">Targets:</label>