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/services/mimestorage.h

@@ -5,8 +5,31 @@
 #include <QString>
 #include <QDir>
 #include <QFile>
+#include <QByteArray>
+#include <QVector>
 #include "core/mailitem.h"
 
+struct ParsedMimeAttachment
+{
+    QString fileName;
+    QString mimeType;
+    QString contentId;
+    QByteArray data;
+};
+
+struct ParsedMimeMessage
+{
+    QString messageId;
+    QString subject;
+    QString from;
+    QString to;
+    QString cc;
+    QString bcc;
+    QDateTime date;
+    QString bodyHtml;
+    QVector<ParsedMimeAttachment> attachments;
+};
+
 class MimeStorageService : public QObject
 {
     Q_OBJECT
@@ -15,16 +38,28 @@ public:
     ~MimeStorageService() override = default;
 
     QString saveEmlFile(const QString &accountId, const QString &folderId, const MailItem &mail);
+    QString saveRawEmlFile(const QString &accountId, const QString &folderId,
+                           const QByteArray &rawMime, const QString &stableId = QString());
+    bool storeMessage(const QString &accountId, const QString &folderId,
+                      MailItem &mail, const QByteArray &rawMime,
+                      QVector<QString> *storedAttachmentPaths = nullptr);
+    bool parseMessage(const QByteArray &rawMime, ParsedMimeMessage &message) const;
     QString getEmlFilePath(const QString &fileId) const;
     QByteArray readEmlFile(const QString &fileId) const;
     bool deleteEmlFile(const QString &fileId);
 
     QStringList listAttachments(const QString &mailItemId) const;
-    bool saveAttachment(const QString &mailItemId, const QString &fileName, const QByteArray &data);
+    QString saveAttachment(const QString &fileId, const QString &fileName,
+                           const QByteArray &data);
 
 private:
     QString storagePath() const;
     QString ensureDirectory(const QString &path) const;
+    QString safeComponent(const QString &value) const;
+    QString decodeHeaderValue(const QString &value) const;
+    QByteArray decodeTransfer(const QByteArray &data, const QString &encoding) const;
+    void parseMimePart(const QByteArray &part, ParsedMimeMessage &message,
+                       QString *plainText, QString *htmlText) const;
 };
 
 #endif // MIMESTORAGESERVICE_H