Add codegen.h header

Add optimize.c - complete optimization pipeline with all passes

Add optimization pass headers

Add ir.c - IR builder, AST-to-IR lowering, and printing

Add IR (intermediate representation) system - ir.h and ir.c

Add parser.c - complete recursive-descent parser for C + parallel extensions

Add parser.h header

Add ast.c - AST construction and debug printing

Add AST header - comprehensive abstract syntax tree definitions

Add lexer.c - full lexical analyzer implementation

Add lexer header and implementation

Add utils.c implementation

Add core header files: utils, lexer, ast