Add MessageBroker for QML and native communication

Introduces MessageBroker to enable communication between the dylib and QML via signals. Updates CMakeLists.txt to include Qml components and conditionally add MessageBroker sources in qmlrebuild mode. reMarkable.m is updated to register the QML type, set up native callbacks, and demonstrate broadcasting signals.

src/reMarkable/reMarkable.m

@@ -7,6 +7,9 @@
 #ifdef BUILD_MODE_DEV
 #import "DevHooks.h"
 #endif
+#ifdef BUILD_MODE_QMLREBUILD
+#import "MessageBroker.h"
+#endif
 #import <objc/runtime.h>
 #import <Cocoa/Cocoa.h>
 #include <stdint.h>
@@ -302,11 +305,25 @@ static inline bool shouldPatchURL(const QString &host) {
 
 #ifdef BUILD_MODE_QMLREBUILD
     NSLogger(@"[reMarkable] Build mode: qmlrebuild");
+    
+    // Register MessageBroker QML type for dylib <-> QML communication
+    messagebroker::registerQmlType();
+    
+    // Register native callback to receive signals from QML
+    messagebroker::setNativeCallback([](const char *signal, const char *value) {
+        NSLogger(@"[reMarkable] Native callback received signal '%s' with value '%s'", signal, value);
+    });
+    
     [MemoryUtils hookSymbol:@"QtCore"
                         symbolName:@"__Z21qRegisterResourceDataiPKhS0_S0_"
                       hookFunction:(void *)hooked_qRegisterResourceData
                   originalFunction:(void **)&original_qRegisterResourceData
                          logPrefix:@"[reMarkable]"];
+
+    // Send a delayed broadcast to QML (after UI has loaded)
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+        messagebroker::broadcast("signalName", "Hello from dylib!");
+    });
 #endif
 
 #ifdef BUILD_MODE_DEV