Feature: HTML export from CLI tool (#11590)

This commit introduces support for exporting a KeePassXC database in
HTML format via the CLI tool. The key changes include:
- Refactoring HtmlExporter:
  - Moved HtmlExporter to the format directory and made its API
    compatible with CsvExporter.
  - Since the original HtmlExporter had a direct dependency on the
    gui/Icons functions and indirect dependencies on the
    gui/DatabaseIcons class, only the non-GUI parts were moved to
    format/HtmlExporter.
  - All icon-related functionality was encapsulated in a new child
    class, gui/HtmlGuiExporter.
    - The gui/HtmlGuiExporter retains the original functionality of the
      HtmlExporter class.
    - The format/HtmlExporter now generates HTML export without icons.
      Adding icon support to format/HtmlExporter would require moving
      icon management logic to the core, which could have broader
      implications.
- CLI integration:
  - Updated cli/Export to use format/HtmlExporter.
- GUI Integration:
  - Updated gui/export/ExportDialog to use gui/HtmlGuiExporter.
- Build System Updates:
  - Updated CMakeLists.txt to build HtmlExporter as part of core_SOURCES
    and HtmlGuiExporter as part of gui_SOURCES.
- Testing:
  - Updated TestCli to automatically verify the output of the HTML
    export.

Signed-off-by: AdriandMartin <adriandmartin@protonmail.com>

tests/TestCli.cpp

@@ -1311,6 +1311,18 @@ void TestCli::testExport()
     QVERIFY(csvData.contains(QByteArray(
         "\"NewDatabase\",\"Sample Entry\",\"User Name\",\"Password\",\"http://www.somesite.com/\",\"Notes\"")));
 
+    // HTML exporting
+    setInput("a");
+    execCmd(exportCmd, {"export", "-f", "html", m_dbFile->fileName()});
+    QByteArray htmlHeader = m_stdout->readLine();
+    QVERIFY(htmlHeader.contains(QByteArray("<meta charset=\"UTF-8\"><title></title>")));
+    QByteArray htmlBody = m_stdout->readAll();
+    QVERIFY(htmlBody.contains(QByteArray("<h2>NewDatabase</h2>")));
+    QVERIFY(htmlBody.contains(QByteArray("<caption>Sample Entry</caption>"
+                                         "<tr><th>User name</th><td class=\"username\">User Name</td></tr>"
+                                         "<tr><th>Password</th><td class=\"password\">Password</td></tr>"
+                                         "<tr><th>URL</th><td class=\"url\"><a "
+                                         "href=\"http://www.somesite.com/\">http://www.somesite.com/</a></td></tr>")));
     // test invalid format
     setInput("a");
     execCmd(exportCmd, {"export", "-f", "yaml", m_dbFile->fileName()});