feat: IMAP sync incremental + Account Setup Wizard + robust FETCH parser

- ImapSynchronizer::syncFolder(): detecta eliminados (UIDs locales no en servidor), fetch nuevos (sinceUid), actualiza flags (FLAGS batch)
- fetchAllUids(): SELECT + SEARCH ALL para lista completa UIDs servidor
- parseAndUpdateFlags(): FETCH FLAGS en lotes 100, update DB si cambió read/flagged
- AccountSetupDialog: integra ConnectionWizard para IMAP/POP3 con test de conexión real
- IMAP FETCH parser robusto: logging respuesta servidor + fallback UID-by-UID
- Fix: FETCH failed logging muestra first/last UID + respuesta truncada

src/db/dao/mailitemdao.h

@@ -5,14 +5,31 @@
 #include <QVector>
 #include <optional>
 
+struct StoredAttachmentRecord
+{
+    QString fileName;
+    QString mimeType;
+    QString contentId;
+    qint64 size{0};
+    QString storedPath;
+};
+
 class MailItemDao
 {
 public:
-    static bool insert(const MailItem& item);
+    static bool insert(MailItem& item);
+    static bool upsert(MailItem& item);
     static bool update(const MailItem& item);
     static bool remove(qint64 id);
     static std::optional<MailItem> findById(qint64 id);
     static QVector<MailItem> findAll();
     static QVector<MailItem> findByFolderId(int folderId);
     static QVector<MailItem> findByFolderIdSinceUid(int folderId, qint64 sinceUid);
-};
+    static std::optional<qint64> maxUidForFolder(int folderId);
+    static QVector<qint64> getUidsForFolder(int folderId);
+    static QVector<qint64> uidsForFolder(int folderId);
+    static std::optional<MailItem> findByUid(int folderId, qint64 uid);
+    static bool removeByUid(int folderId, qint64 uid);
+    static bool replaceAttachments(qint64 mailItemId, const QVector<StoredAttachmentRecord>& attachments);
+    static QVector<StoredAttachmentRecord> attachmentsForMail(qint64 mailItemId);
+};