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/settingsview.cpp

@@ -661,6 +661,22 @@ void SettingsView::setAccountService(AccountService *service) {
     }
 }
 
+void SettingsView::setPreferencesService(PreferencesService *service) {
+    m_preferencesService = service;
+}
+
+void SettingsView::setStartupBehaviorService(StartupBehaviorService *service) {
+    m_startupBehaviorService = service;
+}
+
+void SettingsView::setTranslationService(TranslationService *service) {
+    m_translationService = service;
+}
+
+void SettingsView::setAiActionOptionsService(AiActionOptionsService *service) {
+    m_aiActionOptionsService = service;
+}
+
 void SettingsView::onAccountListChanged() {
     loadAccounts();
 }