feat: Add mouse wheel support for game input passthrough

- Implement mouse wheel event handling in SDL2 backend (emu_window_sdl2)
- Add wheel event routing from GRenderWindow to input subsystem
- Add debugging logs to trace mouse wheel events through input chain
- Support mouse wheel input for mods like Ultracam when games are running (WIP)

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

src/citron/bootmanager.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: 2014 Citra Emulator Project
+// SPDX-FileCopyrightText: 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <algorithm>
@@ -732,6 +733,7 @@ void GRenderWindow::ConstrainMouse() {
 void GRenderWindow::wheelEvent(QWheelEvent* event) {
     const int x = event->angleDelta().x();
     const int y = event->angleDelta().y();
+    LOG_DEBUG(Frontend, "GRenderWindow wheel event: x={}, y={}", x, y);
     input_subsystem->GetMouse()->MouseWheelChange(x, y);
 }