perf(chore): simplify sent grouping, memoize email rows, remove local artifacts

backend/api/emails.py

@@ -322,7 +322,8 @@ async def get_emails(
 
     reply_counts = defaultdict(int)
     thread_messages = defaultdict(list)
-    has_sent_message = {}
+    # ⚡ Bolt: Use a set instead of a dict for boolean tracking to improve semantics and reduce memory.
+    has_sent_message = set()
 
     if grouped:
         thread_lookup: set[str] = set()
@@ -347,13 +348,13 @@ async def get_emails(
             reply_counts[group_key] += 1
             if is_sent_folder and group_key not in has_sent_message:
                 if message_is_from_user(email, user_addresses):
-                    has_sent_message[group_key] = True
+                    has_sent_message.add(group_key)
 
     if is_sent_folder:
         visible_groups = [
             email
             for group_key, email in grouped.items()
-            if has_sent_message.get(group_key, False)
+            if group_key in has_sent_message
         ]
     else:
         visible_groups = list(grouped.values())

frontend/src/components/EmailList.tsx

@@ -1,4 +1,4 @@
-import React, { useCallback, useEffect, useRef, useState, memo } from 'react';
+import React, { useCallback, useEffect, useRef, useState, memo, useMemo } from 'react';
 import { apiClient } from '@/lib/api-client';
 import { ScrollArea } from "@/components/ui/scroll-area";
 import { Avatar, AvatarFallback } from "@/components/ui/avatar";
@@ -173,6 +173,15 @@ export function EmailList({
       };
   const searchBusy = isSearching || loading;
 
+  const emailListContent = useMemo(() => emails.map((email: EmailItem) => (
+    <EmailListItemComponent
+      key={email.id}
+      email={email}
+      selected={selectedEmailId === email.id}
+      onSelectEmail={onSelectEmail}
+    />
+  )), [emails, selectedEmailId, onSelectEmail]);
+
   return (
     <div className="flex h-full min-h-0 w-full flex-col border-r border-border/80 bg-card/95">
       <div className="border-b border-border/80 bg-gradient-to-br from-card via-card to-primary/5 p-4">
@@ -259,14 +268,7 @@ export function EmailList({
               <p className="mt-1 text-xs leading-5">{folderCopy.emptyBody}</p>
             </div>
           ) : (
-            emails.map((email: EmailItem) => (
-              <EmailListItemComponent
-                key={email.id}
-                email={email}
-                selected={selectedEmailId === email.id}
-                onSelectEmail={onSelectEmail}
-              />
-            ))
+            emailListContent
           )}
         </div>
       </ScrollArea>