[Security Assistant] Fix animation border color of security AI assistant (#202319)

## Summary

**Resolves: https://github.com/elastic/kibana/issues/186135**

Changes:
- Update border color of animated border of the security AI assistance
icon from `euiColorPrimary` to `euiBorderColor`.

Old border color:
<img width="182" alt="image"
src="https://github.com/user-attachments/assets/a41a7859-3f9a-488c-bd4f-2ed25a52a481">

New border color:
<img width="169" alt="image"
src="https://github.com/user-attachments/assets/c7e1fa13-adb0-4014-950f-ae643e4e1d6d">
<img width="347" alt="image"
src="https://github.com/user-attachments/assets/8fba05e2-2a5b-48b2-b367-a58162cdaa9e">

New animated:
![Nov-29-2024
13-58-11](https://github.com/user-attachments/assets/2eaaf5a0-9bc2-4d84-9625-11ed7902c2c8)


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

### Identify risks

Does this PR introduce any risks? For example, consider risks like hard
to test bugs, performance regression, potential of data loss.

No

Describe the risk, its severity, and mitigation for each identified
risk. Invite stakeholders and evaluate how to proceed before merging.

- [X] [See some risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx)

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/packages/kbn-elastic-assistant/impl/assistant/assistant_animated_icon.tsx

@@ -7,7 +7,6 @@
 
 import React from 'react';
 import styled from '@emotion/styled';
-import { euiThemeVars } from '@kbn/ui-theme';
 import { AssistantAvatar } from './assistant_avatar/assistant_avatar';
 
 const Container = styled.div`
@@ -18,8 +17,8 @@ const Container = styled.div`
   display: flex;
   justify-content: center;
   align-items: center;
-  margin-top: ${euiThemeVars.euiSizeXXL};
-  margin-bottom: ${euiThemeVars.euiSizeL};
+  margin-top: ${({ theme }) => theme.euiTheme.size.xxl};
+  margin-bottom: ${({ theme }) => theme.euiTheme.size.l};
 
   :before,
   :after {
@@ -45,7 +44,7 @@ const Animation = styled.div`
     top: 0;
     left: 0;
     z-index: 0;
-    border: 1px solid ${euiThemeVars.euiColorPrimary};
+    border: 1px solid ${(props) => props.theme.euiTheme.colors.borderBasePlain};
     border-radius: inherit;
     animation: 4s cubic-bezier(0.42, 0, 0.37, 1) 0.5s infinite normal none running pulsing;
   }

x-pack/packages/kbn-elastic-assistant/impl/data_anonymization_editor/stats/index.tsx

@@ -9,8 +9,8 @@ import { EuiFlexGroup, EuiFlexItem } from '@elastic/eui';
 import { AnonymizationFieldResponse } from '@kbn/elastic-assistant-common/impl/schemas/anonymization_fields/bulk_crud_anonymization_fields_route.gen';
 import { Replacements } from '@kbn/elastic-assistant-common';
 import React, { useMemo } from 'react';
-// eslint-disable-next-line @kbn/eslint/module_migration
-import styled from 'styled-components';
+
+import styled from '@emotion/styled';
 
 import { AllowedStat } from './allowed_stat';
 import { AnonymizedStat } from './anonymized_stat';
@@ -18,7 +18,7 @@ import { getStats } from '../get_stats';
 import { AvailableStat } from './available_stat';
 
 const StatFlexItem = styled(EuiFlexItem)`
-  margin-right: ${({ theme }) => theme.eui.euiSizeL};
+  margin-right: ${({ theme }) => theme.euiTheme.size.l};
 `;
 
 interface Props {

x-pack/packages/kbn-elastic-assistant/impl/mock/test_providers/test_providers.tsx

@@ -8,10 +8,9 @@
 import { httpServiceMock } from '@kbn/core-http-browser-mocks';
 import { I18nProvider } from '@kbn/i18n-react';
 import { actionTypeRegistryMock } from '@kbn/triggers-actions-ui-plugin/public/application/action_type_registry.mock';
-import { euiDarkVars } from '@kbn/ui-theme';
 import React from 'react';
-// eslint-disable-next-line @kbn/eslint/module_migration
-import { ThemeProvider } from 'styled-components';
+
+import { EuiThemeProvider as ThemeProvider } from '@elastic/eui';
 
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
 import { UserProfileService } from '@kbn/core/public';
@@ -67,7 +66,7 @@ export const TestProvidersComponent: React.FC<Props> = ({
 
   return (
     <I18nProvider>
-      <ThemeProvider theme={() => ({ eui: euiDarkVars, darkMode: true })}>
+      <ThemeProvider>
         <QueryClientProvider client={queryClient}>
           <AssistantProvider
             actionTypeRegistry={actionTypeRegistry}

x-pack/packages/kbn-elastic-assistant/tsconfig.json

@@ -12,6 +12,7 @@
   "include": [
     "**/*.ts",
     "**/*.tsx",
+    "../../../typings/emotion.d.ts"
   ],
   "exclude": [
     "target/**/*"