Add tags to all entity types with chip-based input and autocomplete

- Add `tags: List[str]` field to all 13 entity types (devices, output targets,
  CSS sources, picture sources, audio sources, value sources, sync clocks,
  automations, scene presets, capture/audio/PP/pattern templates)
- Update all stores, schemas, and route handlers for tag CRUD
- Add GET /api/v1/tags endpoint aggregating unique tags across all stores
- Create TagInput component with chip display, autocomplete dropdown,
  keyboard navigation, and API-backed suggestions
- Display tag chips on all entity cards (searchable via existing text filter)
- Add tag input to all 14 editor modals with dirty check support
- Add CSS styles and i18n keys (en/ru/zh) for tag UI
- Also includes code review fixes: thread safety, perf, store dedup

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

server/src/wled_controller/storage/postprocessing_template.py

@@ -1,7 +1,7 @@
 """Postprocessing template data model."""
 
 from dataclasses import dataclass, field
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import List, Optional
 
 from wled_controller.core.filters.filter_instance import FilterInstance
@@ -17,6 +17,7 @@ class PostprocessingTemplate:
     created_at: datetime
     updated_at: datetime
     description: Optional[str] = None
+    tags: List[str] = field(default_factory=list)
 
     def to_dict(self) -> dict:
         """Convert template to dictionary."""
@@ -27,6 +28,7 @@ class PostprocessingTemplate:
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),
             "description": self.description,
+            "tags": self.tags,
         }
 
     @classmethod
@@ -40,9 +42,10 @@ class PostprocessingTemplate:
             filters=filters,
             created_at=datetime.fromisoformat(data["created_at"])
             if isinstance(data.get("created_at"), str)
-            else data.get("created_at", datetime.utcnow()),
+            else data.get("created_at", datetime.now(timezone.utc)),
             updated_at=datetime.fromisoformat(data["updated_at"])
             if isinstance(data.get("updated_at"), str)
-            else data.get("updated_at", datetime.utcnow()),
+            else data.get("updated_at", datetime.now(timezone.utc)),
             description=data.get("description"),
+            tags=data.get("tags", []),
         )