Add Settings 'Send Test Digest Email' button (admin) (v0.1.0:75)

Surface the digest test-send endpoint as a clickable admin control so it can be
exercised on the box without curl. Calls POST /api/admin/digest/test-email and
toasts the result (or a 'configure SMTP first' hint). JSX parse-checked.

frontend/index.html

@@ -7768,6 +7768,7 @@
             const [users, setUsers] = useState([]);
             const [usersLoading, setUsersLoading] = useState(false);
             const [userActionLoadingId, setUserActionLoadingId] = useState(null);
+            const [testEmailLoading, setTestEmailLoading] = useState(false);
             const [auditLogs, setAuditLogs] = useState([]);
             const [auditLoading, setAuditLoading] = useState(false);
             const [automationRules, setAutomationRules] = useState([]);
@@ -8216,6 +8217,22 @@
                 }
             };
 
+            const handleSendTestDigestEmail = async () => {
+                setTestEmailLoading(true);
+                try {
+                    const result = await api('/api/admin/digest/test-email', {
+                        method: 'POST',
+                        body: JSON.stringify({})
+                    }, token);
+                    const to = (result?.data?.sent_to || []).join(', ');
+                    onShowToast(`Test digest email sent${to ? ` to ${to}` : ''}`, 'success');
+                } catch (err) {
+                    onShowToast(getErrorMessage(err, 'Failed to send test email — is SMTP configured? (Start9: Configure Digest SMTP, then restart)'), 'error');
+                } finally {
+                    setTestEmailLoading(false);
+                }
+            };
+
             const handleContactsCsvFileUpload = async (event) => {
                 const file = event.target.files && event.target.files[0];
                 if (!file) return;
@@ -8496,6 +8513,16 @@
                                 Invite users and manage fundraising state backups.
                             </div>
 
+                            <div style={{ marginBottom: '20px', borderBottom: '1px solid #263548', paddingBottom: '16px' }}>
+                                <div style={{ fontWeight: 600, marginBottom: '8px' }}>Daily Digest Email</div>
+                                <div style={{ fontSize: '12px', color: '#8ea2b7', marginBottom: '10px' }}>
+                                    Sends a test message to all active admins through the configured SMTP account, to verify outbound email works. Configure SMTP via the Start9 "Configure Digest SMTP" action, then restart the service.
+                                </div>
+                                <button type="button" onClick={handleSendTestDigestEmail} disabled={testEmailLoading}>
+                                    {testEmailLoading ? <Spinner /> : 'Send Test Digest Email'}
+                                </button>
+                            </div>
+
                             <div style={{ marginBottom: '20px', borderBottom: '1px solid #263548', paddingBottom: '16px' }}>
                                 <div style={{ fontWeight: 600, marginBottom: '10px' }}>Invite User</div>
                                 <form onSubmit={handleInviteUser}>