feat: add base model filter to FormDropdown (#8501)

## Summary

Adds a base model filter to the FormDropdown component, allowing users
to filter dropdown options by base model type.

## Changes

- **Base model filter**: New filter popover in FormDropdownMenuActions
that lets users select one or more base models to filter by
- **Clear Filters button**: Added to the base model filter popover for
quick reset
- **Button component refactor**: Replaced native `<button>` elements
with the `Button` component for consistent styling
- **New i18n key**: Added `assets.baseModel` translation

## Files Changed

- `FormDropdownMenuActions.vue` - Main implementation of base model
filter UI
- `WidgetSelectDropdown.vue` - Passes base model options to the dropdown
- `FormDropdown.vue`, `FormDropdownMenu.vue`,
`FormDropdownMenuFilter.vue` - Prop threading
- `filterTypes.ts`, `types.ts` - Type definitions for filter options

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8501-feat-add-base-model-filter-to-FormDropdown-2f96d73d3650813c994debb06070c7dd)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

src/locales/en/main.json

@@ -2506,6 +2506,7 @@
     "imported": "Imported",
     "assetCollection": "Asset collection",
     "assets": "Assets",
+    "baseModel": "Base model",
     "baseModels": "Base models",
     "browseAssets": "Browse Assets",
     "checkpoints": "Checkpoints",