fix: Show all tags in LoRA Pool without limit (#819)

- Backend: Support limit=0 to return all tags in top-tags API
- Frontend: Remove tags limit setting and fetch all tags by default
- UI: Implement virtual scrolling in TagsModal for performance
  - Initial display 200 tags, load more on scroll
  - Show all results when searching
- Remove lora_pool_tags_limit setting to simplify UX

Fixes #819

py/services/model_scanner.py

@@ -1448,7 +1448,7 @@ class ModelScanner:
         return None
         
     async def get_top_tags(self, limit: int = 20) -> List[Dict[str, any]]:
-        """Get top tags sorted by count"""
+        """Get top tags sorted by count. If limit is 0, return all tags."""
         await self.get_cached_data()
         
         sorted_tags = sorted(
@@ -1457,6 +1457,8 @@ class ModelScanner:
             reverse=True
         )
         
+        if limit == 0:
+            return sorted_tags
         return sorted_tags[:limit]
         
     async def get_base_models(self, limit: int = 20) -> List[Dict[str, any]]: