feat: quick actions on email rows (read/unread, star, trash)

- EmailRow shared component with hover action buttons: mark read/unread, star/unstar, trash
- Optimistic UI — local state patches immediately on click; row fades and becomes non-interactive during the API call
- Trashed rows disappear from the current folder view via onRemove callback
- Backend: EmailController single-email endpoints (POST /email/{id}/read|unread|star|unstar|trash|untrash)
- Star/Unstar added to CleanupActionType enum and CleanupService (maps to STARRED Gmail label via BatchModifyAsync)
- UserId scope enforced in ResolveTargetsAsync — a user can only act on their own emails
- action buttons use stopPropagation so clicking them does not open Gmail

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/FolderView.jsx

@@ -1,6 +1,7 @@
 import { useEffect, useState, useCallback, useRef } from 'react';
 import { useParams } from 'react-router-dom';
 import { SearchApi } from '../api/client.js';
+import EmailRow from '../components/EmailRow.jsx';
 
 const FOLDER_META = {
   inbox:      { icon: '📥', label: 'Inbox' },
@@ -31,20 +32,6 @@ const FOLDER_META = {
 
 const PAGE_SIZE = 50;
 
-const fmtDate = (iso) => {
-  const d = new Date(iso);
-  const now = new Date();
-  const diffDays = (now - d) / 86400000;
-  if (diffDays < 1) return d.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });
-  if (diffDays < 7) return d.toLocaleDateString([], { weekday: 'short' });
-  return d.toLocaleDateString([], { month: 'short', day: 'numeric' });
-};
-
-const fmtSize = (b) => {
-  if (b < 1024) return `${b} B`;
-  if (b < 1048576) return `${(b / 1024).toFixed(0)} KB`;
-  return `${(b / 1048576).toFixed(1)} MB`;
-};
 
 export default function FolderView() {
   const { slug } = useParams();
@@ -119,30 +106,11 @@ export default function FolderView() {
         <table className="email-list">
           <tbody>
             {emails.map((e) => (
-              <tr
+              <EmailRow
                 key={e.id}
-                className={`email-row${e.isUnread ? ' email-row--unread' : ''}`}
-                onClick={() => window.open(
-                  `https://mail.google.com/mail/u/0/#all/${e.gmailMessageId}`,
-                  '_blank',
-                  'noopener,noreferrer'
-                )}
-                title="Open in Gmail"
-              >
-                <td className="el-unread">{e.isUnread && <span className="unread-dot" />}</td>
-                <td className="el-sender" title={e.senderAddress}>
-                  {e.senderDisplayName || e.senderAddress}
-                </td>
-                <td className="el-subject">
-                  <span className="el-subj-text">{e.subject || '(no subject)'}</span>
-                  {e.snippet && <span className="el-snippet"> — {e.snippet}</span>}
-                </td>
-                <td className="el-meta">
-                  {e.hasAttachments && <span className="el-attach" title="Has attachment">📎</span>}
-                  {e.sizeEstimateBytes > 1048576 && <span className="el-size">{fmtSize(e.sizeEstimateBytes)}</span>}
-                </td>
-                <td className="el-date">{fmtDate(e.sentAtUtc)}</td>
-              </tr>
+                email={e}
+                onRemove={(id) => setEmails((prev) => prev.filter((x) => x.id !== id))}
+              />
             ))}
           </tbody>
         </table>