Add Account and Folder models, update CMakeLists.txt with source files, add MailItem implementation

src/core/models/account.h

@@ -0,0 +1,55 @@
+#pragma once
+
+#include <QString>
+#include <QDateTime>
+
+enum class AccountType {
+    Outlook,
+    Gmail,
+    IMAP
+};
+
+class Account
+{
+public:
+    Account() = default;
+    Account(int id, const QString& email, const QString& displayName,
+            AccountType type, const QString& accessToken = QString(),
+            const QString& refreshToken = QString(),
+            const QDateTime& tokenExpires = QDateTime());
+
+    int id() const { return m_id; }
+    void setId(int id) { m_id = id; }
+
+    QString email() const { return m_email; }
+    void setEmail(const QString& email) { m_email = email; }
+
+    QString displayName() const { return m_displayName; }
+    void setDisplayName(const QString& displayName) { m_displayName = displayName; }
+
+    AccountType type() const { return m_type; }
+    void setType(AccountType type) { m_type = type; }
+
+    QString accessToken() const { return m_accessToken; }
+    void setAccessToken(const QString& token) { m_accessToken = token; }
+
+    QString refreshToken() const { return m_refreshToken; }
+    void setRefreshToken(const QString& token) { m_refreshToken = token; }
+
+    QDateTime tokenExpires() const { return m_tokenExpires; }
+    void setTokenExpires(const QDateTime& expires) { m_tokenExpires = expires; }
+
+    bool isTokenValid() const {
+        return !m_accessToken.isEmpty() && m_tokenExpires.isValid() &&
+               m_tokenExpires > QDateTime::currentDateTimeUtc();
+    }
+
+private:
+    int m_id{0};
+    QString m_email;
+    QString m_displayName;
+    AccountType m_type{AccountType::IMAP};
+    QString m_accessToken;
+    QString m_refreshToken;
+    QDateTime m_tokenExpires;
+};