Add ambient sound system and eliminate log spam

- Implement AmbientSoundManager with tavern/outdoor ambience
- Fix audio buffer limit (5s → 60s) for long ambient loops
- Set log level to INFO to eliminate DEBUG spam (130MB → 3.2MB logs)
- Remove excessive terrain/model/network logging
- Fix ambient sound timer sharing and pitch parameter bugs

include/audio/activity_sound_manager.hpp

@@ -66,6 +66,7 @@ private:
     std::chrono::steady_clock::time_point lastLandAt{};
     std::chrono::steady_clock::time_point lastSplashAt{};
     std::chrono::steady_clock::time_point lastMeleeSwingAt{};
+    std::chrono::steady_clock::time_point lastSwimStrokeAt{};
     bool meleeSwingWarned = false;
     std::string voiceProfileKey;
     float volumeScale = 1.0f;