Implement technology tree, research queue by least remaining work, and unit/building tech availability & obsolescence

unitconfig.h

@@ -44,6 +44,8 @@ struct UnitConfig {
     int attackRange; // 1 for melee, >1 for ranged
     int buildCharges;
     bool infiniteCharges;
+    QString requiredTech;
+    QString obsoleteTech;
     QString iconPath;
     QStringList actions;
     QMap<QString, float> actionSpeeds; // Duration in seconds per action (e.g. "boerderij_bouwen": 10.0f)
@@ -54,7 +56,7 @@ struct UnitConfig {
         : id(""), name(""), category(UnitCategory::Builder),
           movementDomain(MovementDomain::Land), health(100),
           movementSpeed(2.0f), cost(10), laborCost(1000), attackDamage(0), attackRange(1),
-          buildCharges(-1), infiniteCharges(true), iconPath("") {}
+          buildCharges(-1), infiniteCharges(true), requiredTech(""), obsoleteTech(""), iconPath("") {}
 
     bool isRanged() const { return attackRange > 1; }
     bool isMilitary() const { return category == UnitCategory::Military; }