Add BetterCam engine, UI polish, and bug fixes

- Add BetterCam capture engine (DXGI Desktop Duplication, priority 4)
- Fix missing picture_stream_id in get_device endpoint
- Fix template delete validation to check streams instead of devices
- Add description field to capture engine template UI
- Default template name changed to "Default" with descriptive text
- Display picker highlights selected display instead of primary
- Fix modals closing when dragging text selection outside dialog
- Rename "Engine Configuration" to "Configuration", hide when empty
- Rename "Run Test" to "Run" across all test buttons
- Always reserve space for vertical scrollbar
- Redesign Stream Settings info panel with pill-style props
- Fix processed stream showing internal ID instead of stream name
- Update en/ru locale files

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

server/src/wled_controller/storage/template_store.py

@@ -49,12 +49,12 @@ class TemplateStore:
 
         template = CaptureTemplate(
             id=template_id,
-            name=best_engine.upper(),
+            name="Default",
             engine_type=best_engine,
             engine_config=default_config,
             created_at=now,
             updated_at=now,
-            description=f"Auto-created {best_engine.upper()} template",
+            description=f"Default capture template using {best_engine.upper()} engine",
         )
 
         self._templates[template_id] = template