feat: implement for-loops with proper scope management

- Add support for C-style for loops: for (init; condition; increment) { body }
- Implement three-level scoping: loop context + per-iteration contexts
- Add semicolon disabler for increment statements using RAII guards
- Support break/continue/return control flow with scope validation
- Fix semicolon handling in parser for flexible for-loop syntax

include/evaluator.hpp

@@ -111,6 +111,7 @@ namespace Fig
         Value evalBinary(const Ast::BinaryExpr &);
         Value evalUnary(const Ast::UnaryExpr &);
 
+        StatementResult evalBlockStatement(const Ast::BlockStatement &, ContextPtr = nullptr);
         StatementResult evalStatement(const Ast::Statement &);
 
         Value evalFunctionCall(const Function &, const Ast::FunctionArguments &, FString fnName = u8"<anonymous>");