feat: Add Firebase high score sync, menu music, and gameplay improvements

- Integrate Firebase Realtime Database for high score synchronization
  - Add cpr and nlohmann-json dependencies for HTTP requests
  - Implement async score loading from Firebase with local fallback
  - Submit all scores > 0 to Firebase in background thread
  - Always prompt for player name on game over if score > 0

- Add dedicated menu music system
  - Implement menu track support in Audio class with looping
  - Add "Every Block You Take.mp3" as main menu theme
  - Automatically switch between menu and game music on state transitions
  - Load menu track asynchronously to prevent startup delays

- Update level speed progression to match web version
  - Replace NES frame-based gravity with explicit millisecond values
  - Implement 20-level speed table (1000ms to 60ms)
  - Ensure consistent gameplay between C++ and web versions

- Fix startup performance issues
  - Move score loading to background thread to prevent UI freeze
  - Optimize Firebase network requests with 2s timeout
  - Add graceful fallback to local scores on network failure

Files modified:
- src/persistence/Scores.cpp/h - Firebase integration
- src/audio/Audio.cpp/h - Menu music support
- src/core/GravityManager.cpp/h - Level speed updates
- src/main.cpp - State-based music switching, async loading
- CMakeLists.txt - Add cpr and nlohmann-json dependencies
- vcpkg.json - Update dependency list

src/audio/Audio.cpp

@@ -104,25 +104,52 @@ void Audio::feed(Uint32 bytesWanted, SDL_AudioStream* stream){
     std::vector<int16_t> mix(outSamples, 0);
 
     // 1) Mix music into buffer (if not muted)
-    if(!muted && current >= 0){
+    // 1) Mix music into buffer (if not muted)
+    if(!muted && playing){
         size_t cursorBytes = 0;
         while(cursorBytes < bytesWanted){
-            if(current < 0) break;
-            auto &trk = tracks[current];
-            size_t samplesAvail = trk.pcm.size() - trk.cursor; // samples (int16)
-            if(samplesAvail == 0){ nextTrack(); if(current < 0) break; continue; }
+            AudioTrack* trk = nullptr;
+            
+            if (isMenuMusic) {
+                if (menuTrack.ok) trk = &menuTrack;
+            } else {
+                if (current >= 0 && current < (int)tracks.size()) trk = &tracks[current];
+            }
+            
+            if (!trk) break;
+
+            size_t samplesAvail = trk->pcm.size() - trk->cursor; // samples (int16)
+            if(samplesAvail == 0){ 
+                if (isMenuMusic) {
+                    trk->cursor = 0; // Loop menu music
+                    continue;
+                } else {
+                    nextTrack(); 
+                    if(current < 0) break; 
+                    continue; 
+                }
+            }
+            
             size_t samplesNeeded = (bytesWanted - cursorBytes) / sizeof(int16_t);
             size_t toCopy = (samplesAvail < samplesNeeded) ? samplesAvail : samplesNeeded;
             if(toCopy == 0) break;
+            
             // Mix add with clamp
             size_t startSample = cursorBytes / sizeof(int16_t);
             for(size_t i=0;i<toCopy;++i){
-                int v = (int)mix[startSample+i] + (int)trk.pcm[trk.cursor+i];
+                int v = (int)mix[startSample+i] + (int)trk->pcm[trk->cursor+i];
                 if(v>32767) v=32767; if(v<-32768) v=-32768; mix[startSample+i] = (int16_t)v;
             }
-            trk.cursor += toCopy;
+            trk->cursor += toCopy;
             cursorBytes += (Uint32)(toCopy * sizeof(int16_t));
-            if(trk.cursor >= trk.pcm.size()) nextTrack();
+            
+            if(trk->cursor >= trk->pcm.size()) {
+                if (isMenuMusic) {
+                    trk->cursor = 0; // Loop menu music
+                } else {
+                    nextTrack();
+                }
+            }
         }
     }
 
@@ -266,6 +293,39 @@ int Audio::getLoadedTrackCount() const {
     return loadedCount;
 }
 
+void Audio::setMenuTrack(const std::string& path) {
+    menuTrack.path = path;
+#ifdef _WIN32
+    // Ensure MF is started (might be redundant if init called, but safe)
+    if(!mfStarted){ if(FAILED(MFStartup(MF_VERSION))) { SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "[Audio] MFStartup failed"); } else mfStarted=true; }
+    
+    if (decodeMP3(path, menuTrack.pcm, menuTrack.rate, menuTrack.channels)) {
+        menuTrack.ok = true;
+    } else {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "[Audio] Failed to decode menu track %s", path.c_str());
+    }
+#else
+    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "[Audio] MP3 unsupported (stub): %s", path.c_str());
+#endif
+}
+
+void Audio::playMenuMusic() {
+    isMenuMusic = true;
+    if (menuTrack.ok) {
+        menuTrack.cursor = 0;
+    }
+    start();
+}
+
+void Audio::playGameMusic() {
+    isMenuMusic = false;
+    // If we were playing menu music, we might want to pick a random track or resume
+    if (current < 0 && !tracks.empty()) {
+        nextTrack();
+    }
+    start();
+}
+
 void Audio::shutdown(){ 
     // Stop background loading thread first
     if (loadingThread.joinable()) {