feat: Implement Qt6 migration with aqtinstall 3.3.0

- Migrate from Qt5 to Qt6.7.3 using aqtinstall v3.3.0
- Add comprehensive Qt6 API compatibility updates
- Implement responsive UI with High DPI scaling support
- Add MSVC runtime library configuration for consistency
- Update touch/mouse event handling for Qt6 APIs
- Fix locale handling (countryToString → territoryToString)
- Update string size methods (count() → size())
- Remove deprecated Qt5 high DPI attributes
- Add new CopyCitronQt6Deps.cmake for Qt6 dependency management
- Update CMake configuration for Qt6-only approach
- Add aqt_config.ini with mirror configuration for reliable downloads

Signed-off-by: Zephyron <zephyron@citron-emu.org>

CMakeModules/aqt_config.ini

@@ -0,0 +1,31 @@
+# SPDX-FileCopyrightText: 2025 citron Emulator Project
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+[aqt]
+concurrency: 4
+
+[mirrors]
+trusted_mirrors:
+    https://download.qt.io
+blacklist:
+    https://qt.mirror.constant.com
+    https://mirrors.ocf.berkeley.edu
+    https://mirrors.ustc.edu.cn
+    https://mirrors.tuna.tsinghua.edu.cn
+    https://mirrors.geekpie.club
+    https://mirrors-wan.geekpie.club
+    https://mirrors.sjtug.sjtu.edu.cn
+fallbacks:
+    https://qtproject.mirror.liquidtelecom.com/
+    https://mirrors.aliyun.com/qt/
+    https://ftp.jaist.ac.jp/pub/qtproject/
+    https://ftp.yz.yamagata-u.ac.jp/pub/qtproject/
+    https://qt-mirror.dannhauer.de/
+    https://ftp.fau.de/qtproject/
+    https://mirror.netcologne.de/qtproject/
+    https://mirrors.dotsrc.org/qtproject/
+    https://www.nic.funet.fi/pub/mirrors/download.qt-project.org/
+    https://master.qt.io/
+    https://mirrors.ukfast.co.uk/sites/qt.io/
+    https://ftp2.nluug.nl/languages/qt/
+    https://ftp1.nluug.nl/languages/qt/