fix: remove all MUI dependencies causing plugin load failure

Replace all @mui/material and @mui/icons-material imports with standard
HTML elements and inline styles. This fixes the browser error:
"TypeError: undefined is not an object (evaluating 'q.createSvgIcon')"

The Headlamp plugin environment doesn't provide the full MUI library,
so plugins must use only Headlamp CommonComponents or standard HTML.

Changes:
- AppBarScoreBadge: Replace Chip and ShieldIcon with button and emoji
- DashboardView: Replace Button and RefreshIcon with button and emoji
- ExemptionManager: Replace all MUI form components with HTML equivalents
- PolarisSettings: Replace Button with HTML button

All tests passing (50/50), TypeScript compilation clean, build successful.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

src/components/PolarisSettings.tsx

@@ -4,7 +4,6 @@ import {
   StatusLabel,
 } from '@kinvolk/headlamp-plugin/lib/CommonComponents';
 import { ApiProxy } from '@kinvolk/headlamp-plugin/lib';
-import { Button } from '@mui/material';
 import React from 'react';
 import {
   getDashboardUrl,
@@ -124,14 +123,22 @@ export default function PolarisSettings(props: PluginSettingsProps) {
             name: 'Connection Test',
             value: (
               <div>
-                <Button
-                  variant="contained"
+                <button
                   onClick={testConnection}
                   disabled={testing}
-                  size="small"
+                  style={{
+                    padding: '6px 16px',
+                    backgroundColor: testing ? '#ccc' : '#1976d2',
+                    color: 'white',
+                    border: 'none',
+                    borderRadius: '4px',
+                    cursor: testing ? 'not-allowed' : 'pointer',
+                    fontSize: '13px',
+                    fontWeight: 500,
+                  }}
                 >
                   {testing ? 'Testing...' : 'Test Connection'}
-                </Button>
+                </button>
                 {testResult && (
                   <div style={{ marginTop: '8px' }}>
                     <StatusLabel status={testResult.success ? 'success' : 'error'}>