feat: match Code Interpreter file upload to the File Search dropzone

Swap Code Interpreter's thin btn-neutral bar for the same dashed dropzone
(DropzoneContent + dropzoneClassName) File Search already uses, so the two
capabilities' upload UIs are consistent.

client/src/components/SidePanel/Agents/Code/Files.tsx

@@ -1,10 +1,10 @@
 import { memo, useMemo, useRef, useState } from 'react';
 import { useFormContext } from 'react-hook-form';
-import { AttachmentIcon } from '@librechat/client';
 import { EToolResources, EModelEndpoint, AgentCapabilities } from 'librechat-data-provider';
 import type { ExtendedFile, AgentForm } from '~/common';
 import { useFileHandlingNoChatContext } from '~/hooks/Files/useFileHandling';
 import { useAgentFileConfig, useLocalize, useLazyEffect } from '~/hooks';
+import DropzoneContent, { dropzoneClassName } from '../UploadDropzone';
 import FileRow from '~/components/Chat/Input/Files/FileRow';
 import { isEphemeralAgent } from '~/common';
 
@@ -87,23 +87,23 @@ function Files({
           <button
             type="button"
             disabled={uploadDisabled}
-            className="btn btn-neutral border-token-border-light relative h-9 w-full rounded-lg text-sm font-medium"
+            className={dropzoneClassName}
             onClick={handleButtonClick}
           >
-            <div className="flex w-full items-center justify-center gap-1">
-              <input
-                multiple={true}
-                type="file"
-                style={{ display: 'none' }}
-                tabIndex={-1}
-                ref={fileInputRef}
-                disabled={uploadDisabled}
-                onChange={handleFileUpload}
-              />
-              <AttachmentIcon className="text-token-text-primary h-4 w-4" />
-              {localize('com_ui_upload_code_environment')}
-            </div>
+            <DropzoneContent
+              label={localize('com_ui_upload_code_environment')}
+              hint={localize('com_ui_upload_files_hint')}
+            />
           </button>
+          <input
+            multiple={true}
+            type="file"
+            style={{ display: 'none' }}
+            tabIndex={-1}
+            ref={fileInputRef}
+            disabled={uploadDisabled}
+            onChange={handleFileUpload}
+          />
         </div>
       </div>
     </div>