feat(ui): merge user tags into auto-tag badges and refresh on tag edit (#918)

- Layer 2 fallback: user tags overlapping with auto-tag categories
  (HIGH/LOW/I2V/T2V/TI2V/Lightning/Turbo) are merged into auto_tags,
  providing manual override when filename-based detection fails.
  Matching is case-insensitive so "high"/"High"/"HIGH" all work.
- Refresh on tag edit: save_metadata and add_tags handlers now return
  recalculated auto_tags in the response; the frontend passes them to
  VirtualScroller.updateSingleItem so badges update immediately without
  requiring a page reload.
- 8 new test cases for Layer 2 fallback and case-insensitive matching.

tests/services/test_route_support_services.py

@@ -255,7 +255,7 @@ def test_tag_update_service_adds_unique_tags(tmp_path: Path) -> None:
         cache_updates.append(metadata)
         return True
 
-    tags = asyncio.run(
+    tags, auto_tags = asyncio.run(
         service.add_tags(
             file_path=str(tmp_path / "model.safetensors"),
             new_tags=["new", "existing"],
@@ -265,5 +265,6 @@ def test_tag_update_service_adds_unique_tags(tmp_path: Path) -> None:
     )
 
     assert tags == ["existing", "new"]
+    assert auto_tags == []
     assert manager.saved
     assert cache_updates