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/main.py

@@ -188,19 +188,6 @@ async def lifespan(app: FastAPI):
     # Start auto-backup engine (periodic configuration backups)
     await auto_backup_engine.start()
 
-    # Auto-start targets with auto_start=True
-    auto_started = 0
-    for target in targets:
-        if getattr(target, "auto_start", False):
-            try:
-                await processor_manager.start_processing(target.id)
-                auto_started += 1
-                logger.info(f"Auto-started target: {target.name} ({target.id})")
-            except Exception as e:
-                logger.warning(f"Failed to auto-start target {target.id}: {e}")
-    if auto_started:
-        logger.info(f"Auto-started {auto_started} target(s)")
-
     yield
 
     # Shutdown