fix(ui): unify HF file selection UI, remove cloud icon, add select-all, cleanup dead code (#965, #977)

- Unify single-URL and multi-URL HF repo flows to use the same batch
  preview interface (remove separate repoFileStep)
- Remove unnecessary cloud icon from HF batch preview items
- Use formatFileSize() instead of hardcoded MB text
- Change default selection to unchecked (no preselected files)
- Add select all / deselect all checkbox with dynamic Next button
- Clean up dead CSS, HTML template, and JS methods from removed
  repoFileStep
- Add selectAll i18n key with translations for all 10 locales
- Fix batch progress bar name fallback for HF items

locales/es.json

@@ -1136,6 +1136,7 @@
       "placeholder": "https://civitai.com/models/...",
       "urlHint": "Ingrese una URL de CivitAI, CivArchive o Hugging Face por línea. Admite múltiples URLs para descarga por lotes.",
       "selectHfFiles": "Seleccione el/los archivo(s) para descargar de este repositorio:",
+      "selectAll": "Seleccionar todo",
       "fetchingRepoFiles": "Obteniendo archivos del repositorio...",
       "locationPreview": "Vista previa de ubicación de descarga",
       "useDefaultPath": "Usar ruta predeterminada",