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/storage/picture_target.py

@@ -15,7 +15,6 @@ class PictureTarget:
     created_at: datetime
     updated_at: datetime
     description: Optional[str] = None
-    auto_start: bool = False
 
     def register_with_manager(self, manager) -> None:
         """Register this target with the processor manager. Subclasses override."""
@@ -27,14 +26,12 @@ class PictureTarget:
 
     def update_fields(self, *, name=None, device_id=None, picture_source_id=None,
                       settings=None, key_colors_settings=None, description=None,
-                      auto_start=None) -> None:
+                      **_kwargs) -> None:
         """Apply mutable field updates. Base handles common fields; subclasses handle type-specific ones."""
         if name is not None:
             self.name = name
         if description is not None:
             self.description = description
-        if auto_start is not None:
-            self.auto_start = auto_start
 
     @property
     def has_picture_source(self) -> bool:
@@ -48,7 +45,6 @@ class PictureTarget:
             "name": self.name,
             "target_type": self.target_type,
             "description": self.description,
-            "auto_start": self.auto_start,
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),
         }