Implement config-driven unlock groups so that multiple things can be unlocked at once (including buildings)

src/lib/config/RecipesConfig.h

@@ -32,14 +32,12 @@ struct RecipeDef
     std::vector<RecipeIngredient> inputs;
     std::vector<RecipeOutput> outputs;
     double durationSeconds;
-    // Assembler only. nullopt = implicit-only locking. -1 = explicitly unlocked
-    // at game start. >= 0 = locked; schematic enters drop pool at that station
-    // level once the output item is implicitly unlocked (REQ-LOCK-EXPLICIT).
-    std::optional<int> unlockAtStationLevel;
-    // Assembler recipe schematics only. Prerequisite schematic ids that must be
-    // explicitly unlocked before this schematic can enter the drop pool
-    // (REQ-LOCK-PREREQ). Empty = none.
-    std::vector<std::string> unlockRequires;
+    // Assembler only. When true, this recipe is available from game start
+    // regardless of the implicit item graph — used for base recipes that no
+    // schematic's materials reach (e.g. building blocks). See REQ-LOCK-IMPLICIT.
+    // Otherwise an assembler recipe is either explicitly gated (granted by an
+    // unlock group, REQ-LOCK-EXPLICIT) or implicitly gated via the item graph.
+    bool unlockedAtStart = false;
 };
 
 struct RecipesConfig