Implement LLVM backend basic structure - Phase 9.78 Week 1 foundation

Co-authored-by: moe-charm <217100418+moe-charm@users.noreply.github.com>

src/backend/llvm/mod.rs

@@ -0,0 +1,42 @@
+/*!
+ * LLVM Backend Module - Compile MIR to LLVM IR for AOT execution
+ * 
+ * This module provides LLVM-based compilation of Nyash MIR to native code.
+ * Phase 9.78 PoC implementation focused on minimal "return 42" support.
+ */
+
+pub mod context;
+pub mod compiler;
+
+use crate::mir::function::MirModule;
+use crate::box_trait::{NyashBox, IntegerBox};
+
+/// Compile MIR module to object file and execute
+pub fn compile_and_execute(
+    mir_module: &MirModule,
+    output_path: &str,
+) -> Result<Box<dyn NyashBox>, String> {
+    let compiler = compiler::LLVMCompiler::new()?;
+    compiler.compile_and_execute(mir_module, output_path)
+}
+
+/// Compile MIR module to object file only
+pub fn compile_to_object(
+    mir_module: &MirModule,
+    output_path: &str,
+) -> Result<(), String> {
+    let compiler = compiler::LLVMCompiler::new()?;
+    compiler.compile_module(mir_module, output_path)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    
+    #[test]
+    fn test_llvm_module_creation() {
+        // Basic test to ensure the module can be loaded
+        // Actual compilation tests require full MIR infrastructure
+        assert!(true);
+    }
+}