Implement city production projects for units and buildings

city.h

@@ -18,6 +18,29 @@ struct CityYieldSummary {
     int gold = 0;
 };
 
+enum class CityProjectType {
+    None,
+    Unit,
+    Building
+};
+
+struct CityProject {
+    CityProjectType type = CityProjectType::None;
+    QString id = "";
+    QString name = "";
+    int laborCost = 0;
+    int currentLabor = 0;
+    QString district = "center";
+
+    bool isValid() const { return type != CityProjectType::None && !id.isEmpty(); }
+    float getProgress() const {
+        return laborCost > 0 ? std::max(0.0f, std::min(1.0f, (float)currentLabor / (float)laborCost)) : 0.0f;
+    }
+    int getRemainingLabor() const {
+        return std::max(0, laborCost - currentLabor);
+    }
+};
+
 class City {
 public:
     int id;
@@ -31,12 +54,45 @@ public:
     int inhabitantsPerPop;
     int accumulatedLabor = 0; // Local resource (Arbeid)
 
+    CityProject currentProject;
+    std::vector<QString> completedBuildings; // IDs of completed buildings in the city
+
     std::vector<std::pair<int, int>> territory; // Owned hex coordinates
     std::map<std::pair<int, int>, QString> workedTiles; // (x, y) -> resource name
 
     City(int cId, int pId, const QString &cName, int tx, int ty, const QVector3D &pos,
          int initInhabitants = 1000, int initInhabitantsPerPop = 100000, int initRadius = 1);
 
+    bool hasBuilding(const QString &buildingId) const {
+        for (const auto &b : completedBuildings) {
+            if (b == buildingId) return true;
+        }
+        return false;
+    }
+
+    bool addBuilding(const QString &buildingId) {
+        if (hasBuilding(buildingId)) return false;
+        completedBuildings.push_back(buildingId);
+        return true;
+    }
+
+    bool hasActiveProject() const {
+        return currentProject.isValid();
+    }
+
+    void startProject(CityProjectType type, const QString &projId, const QString &projName, int cost, const QString &district = "center") {
+        currentProject.type = type;
+        currentProject.id = projId;
+        currentProject.name = projName;
+        currentProject.laborCost = std::max(1, cost);
+        currentProject.currentLabor = 0;
+        currentProject.district = district.isEmpty() ? "center" : district;
+    }
+
+    void cancelProject() {
+        currentProject = CityProject();
+    }
+
     bool addTerritory(int tx, int ty) {
         if (ownsTile(tx, ty)) return false;
         territory.emplace_back(tx, ty);