init: initial commit of the Scarlett framework

- Initialize Rust project configuration (Cargo) and .gitignore
- Implement core Intermediate Representation (IR), printer, and builder
utilities
- Add IR validation module for type checking and constraint verification
- Introduce optimization passes: Mem2Reg, Constant Folding, Copy
Propagation, Dead Code Elimination, and SSA Destruction
- Implement x86_64 backend for assembly code generation
- Add a C test harness and main entry point to generate, compile, and
test a GCD assembly function

.gitignore

@@ -0,0 +1 @@
+/target