feat: Implement input management system with SDL2 support

- Introduced a new input management system utilizing SDL2 for continuous polling of SNES controller states, enhancing responsiveness and gameplay experience.
- Replaced the previous ImGui-based event handling with a more robust input manager that supports multiple backends and configurations.
- Added a dedicated input backend for SDL2, allowing for flexible key mapping and improved input handling.
- Updated the Emulator class to integrate the new input manager, ensuring seamless interaction with the emulator's UI and game logic.
- Refactored keyboard configuration UI to facilitate easy remapping of SNES controller buttons, improving user accessibility.

src/app/emu/input/input_manager.cc

@@ -0,0 +1,83 @@
+#include "app/emu/input/input_manager.h"
+
+#include "app/emu/snes.h"
+#include "util/log.h"
+
+namespace yaze {
+namespace emu {
+namespace input {
+
+bool InputManager::Initialize(InputBackendFactory::BackendType type) {
+  backend_ = InputBackendFactory::Create(type);
+  if (!backend_) {
+    LOG_ERROR("InputManager", "Failed to create input backend");
+    return false;
+  }
+  
+  InputConfig config;
+  config.continuous_polling = true;  // Always use continuous polling for games
+  config.enable_gamepad = false;      // TODO: Enable when gamepad support added
+  
+  if (!backend_->Initialize(config)) {
+    LOG_ERROR("InputManager", "Failed to initialize input backend");
+    return false;
+  }
+  
+  LOG_INFO("InputManager", "Initialized with backend: %s", 
+           backend_->GetBackendName().c_str());
+  return true;
+}
+
+void InputManager::Initialize(std::unique_ptr<IInputBackend> backend) {
+  backend_ = std::move(backend);
+  
+  if (backend_) {
+    LOG_INFO("InputManager", "Initialized with custom backend: %s",
+             backend_->GetBackendName().c_str());
+  }
+}
+
+void InputManager::Shutdown() {
+  if (backend_) {
+    backend_->Shutdown();
+    backend_.reset();
+  }
+}
+
+void InputManager::Poll(Snes* snes, int player) {
+  if (!snes || !backend_) return;
+  
+  // Poll backend for current controller state
+  ControllerState state = backend_->Poll(player);
+  
+  // Update SNES controller state using the hardware button layout
+  // SNES controller bits: 0=B, 1=Y, 2=Select, 3=Start, 4-7=DPad, 8=A, 9=X, 10=L, 11=R
+  for (int i = 0; i < 12; i++) {
+    bool pressed = (state.buttons & (1 << i)) != 0;
+    snes->SetButtonState(player, i, pressed);
+  }
+}
+
+void InputManager::ProcessEvent(void* event) {
+  if (backend_) {
+    backend_->ProcessEvent(event);
+  }
+}
+
+InputConfig InputManager::GetConfig() const {
+  if (backend_) {
+    return backend_->GetConfig();
+  }
+  return InputConfig{};
+}
+
+void InputManager::SetConfig(const InputConfig& config) {
+  if (backend_) {
+    backend_->SetConfig(config);
+  }
+}
+
+}  // namespace input
+}  // namespace emu
+}  // namespace yaze
+