feat: Search Online (IMAP) + real Calendar/Contacts UI + iCloud auth wiring

Search Online:
- Synchronizer::searchOnline(folderId, query) virtual with default {}
- ImapSynchronizer: SELECT + UID SEARCH (Subject/From/To/TEXT) + fetch results
- MailService::searchOnline() + onlineSearchFinished/onlineSearchError signals
- MainMainWindow::onOnlineSearchRequested shows real server results

Calendar:
- Real QCalendarWidget view with per-day agenda from local mails
- New MailItemDao::findByDateRange(start, end)

Contacts:
- QTableWidget aggregating addresses from all local mails
- Regex email extraction + live search filter

iCloud/AccountService:
- Wire IcloudAuthenticator into AccountService::createAuthenticator

src/ui/accountsetupdialog.cpp

@@ -193,6 +193,7 @@ QWidget* AccountSetupDialog::createProviderPage()
 
     lay->addWidget(makeRadio("🔴  Google / Gmail",         "OAuth2 seguro",           0));
     lay->addWidget(makeRadio("🔵  Microsoft / Outlook",    "OAuth2 seguro",           1));
+    lay->addWidget(makeRadio("☁️  iCloud / Apple",         "OAuth2 seguro (Apple ID)",  3));
     lay->addWidget(makeRadio("⚙️  IMAP / SMTP",            "Servidor personalizado",  2));
 
     m_providerGroup->button(0)->setChecked(true);
@@ -430,6 +431,9 @@ void AccountSetupDialog::onNextClicked()
         if (m_selectedProvider == 2) {
             // Launch ConnectionWizard for IMAP/POP3 setup
             launchConnectionWizard();
+        } else if (m_selectedProvider == 3) {
+            // iCloud - use OAuth2 flow like Gmail/Outlook
+            goToPage(PageOAuth);
         } else {
             // Update OAuth page subtitle based on provider
             goToPage(PageOAuth);
@@ -486,7 +490,11 @@ void AccountSetupDialog::startOAuthAuthentication()
     m_oauthStatusLabel->setText("Abriendo navegador… Completa el inicio de sesión allí.");
     m_oauthStatusLabel->setStyleSheet("font-size: 12px; color: #0071e3; font-weight: 600;");
 
-    QString provider = (m_selectedProvider == 0) ? "gmail" : "outlook";
+    QString provider;
+    if (m_selectedProvider == 0) provider = "gmail";
+    else if (m_selectedProvider == 1) provider = "outlook";
+    else if (m_selectedProvider == 3) provider = "icloud";
+    else provider = "gmail"; // fallback
 
     // Start authentication via AccountService (opens browser)
     m_accountService->startAuthentication(email, provider);