feat(richtext-lexical): support copy & pasting and drag & dopping files/images into the editor (#13868)

This PR adds support for inserting images into the rich text editor via
both **copy & paste** and **drag & drop**, whether from local files or
image DOM nodes.

It leverages the bulk uploads UI to provide a smooth workflow for:
- Selecting the target collection
- Filling in any required fields defined on the uploads collection
- Uploading multiple images at once

This significantly improves the UX for adding images to rich text, and
also works seamlessly when pasting images from external editors like
Google Docs or Microsoft Word.

Test pre-release: `3.57.0-internal.801ab5a`

## Showcase - drag & drop images from computer


https://github.com/user-attachments/assets/c558c034-d2e4-40d8-9035-c0681389fb7b

## Showcase - copy & paste images from computer


https://github.com/user-attachments/assets/f36faf94-5274-4151-b141-00aff2b0efa4

## Showcase - copy & paste image DOM nodes


https://github.com/user-attachments/assets/2839ed0f-3f28-4e8d-8b47-01d0cb947edc

---
- To see the specific tasks where the Asana app for GitHub is being
used, see below:
  - https://app.asana.com/0/0/1211217132290841

packages/ui/src/elements/BulkUpload/FileSidebar/index.tsx

@@ -5,8 +5,10 @@ import { useWindowInfo } from '@faceless-ui/window-info'
 import { isImage } from 'payload/shared'
 import React from 'react'
 
+import { SelectInput } from '../../../fields/Select/Input.js'
 import { ChevronIcon } from '../../../icons/Chevron/index.js'
 import { XIcon } from '../../../icons/X/index.js'
+import { useConfig } from '../../../providers/Config/index.js'
 import { useTranslation } from '../../../providers/Translation/index.js'
 import { AnimateHeight } from '../../AnimateHeight/index.js'
 import { Button } from '../../Button/index.js'
@@ -18,9 +20,9 @@ import { createThumbnail } from '../../Thumbnail/createThumbnail.js'
 import { Thumbnail } from '../../Thumbnail/index.js'
 import { Actions } from '../ActionsBar/index.js'
 import { AddFilesView } from '../AddFilesView/index.js'
+import './index.scss'
 import { useFormsManager } from '../FormsManager/index.js'
 import { useBulkUpload } from '../index.js'
-import './index.scss'
 
 const addMoreFilesDrawerSlug = 'bulk-upload-drawer--add-more-files'
 
@@ -36,7 +38,7 @@ export function FileSidebar() {
     setActiveIndex,
     totalErrorCount,
   } = useFormsManager()
-  const { initialFiles, maxFiles } = useBulkUpload()
+  const { initialFiles, initialForms, maxFiles } = useBulkUpload()
   const { i18n, t } = useTranslation()
   const { closeModal, openModal } = useModal()
   const [showFiles, setShowFiles] = React.useState(false)
@@ -66,7 +68,17 @@ export function FileSidebar() {
     return formattedSize
   }, [])
 
-  const totalFileCount = isInitializing ? initialFiles.length : forms.length
+  const totalFileCount = isInitializing
+    ? (initialFiles?.length ?? initialForms?.length)
+    : forms.length
+
+  const {
+    collectionSlug: bulkUploadCollectionSlug,
+    selectableCollections,
+    setCollectionSlug,
+  } = useBulkUpload()
+
+  const { getEntityConfig } = useConfig()
 
   return (
     <div
@@ -74,6 +86,29 @@ export function FileSidebar() {
     >
       {breakpoints.m && showFiles ? <div className={`${baseClass}__mobileBlur`} /> : null}
       <div className={`${baseClass}__header`}>
+        {selectableCollections?.length > 1 && (
+          <SelectInput
+            className={`${baseClass}__collectionSelect`}
+            isClearable={false}
+            name="groupBy"
+            onChange={(e) => {
+              const val: string =
+                typeof e === 'object' && 'value' in e
+                  ? (e?.value as string)
+                  : (e as unknown as string)
+              setCollectionSlug(val)
+            }}
+            options={
+              selectableCollections?.map((coll) => {
+                const config = getEntityConfig({ collectionSlug: coll })
+                return { label: config.labels.singular, value: config.slug }
+              }) || []
+            }
+            path="groupBy"
+            required
+            value={bulkUploadCollectionSlug}
+          />
+        )}
         <div className={`${baseClass}__headerTopRow`}>
           <div className={`${baseClass}__header__text`}>
             <ErrorPill count={totalErrorCount} i18n={i18n} withMessage />
@@ -130,8 +165,10 @@ export function FileSidebar() {
       <div className={`${baseClass}__animateWrapper`}>
         <AnimateHeight height={!breakpoints.m || showFiles ? 'auto' : 0}>
           <div className={`${baseClass}__filesContainer`}>
-            {isInitializing && forms.length === 0 && initialFiles.length > 0
-              ? Array.from(initialFiles).map((file, index) => (
+            {isInitializing &&
+            forms.length === 0 &&
+            (initialFiles?.length > 0 || initialForms?.length > 0)
+              ? (initialFiles ? Array.from(initialFiles) : initialForms).map((file, index) => (
                   <ShimmerEffect
                     animationDelay={`calc(${index} * ${60}ms)`}
                     height="35px"