Refactor into generic SQL template framework

- Replace hardcoded Person struct with dynamic column handling
- Add configurable directives: sqlite_db, sqlite_query, sqlite_template
- Support arbitrary SQL queries with any table/column structure
- Create generic execute_query() function returning dynamic JSON data
- Update handler to render templates with configurable paths
- Add build.rs for macOS dynamic linking support
- Fix handler return value to prevent 'header already sent' errors

build.rs

@@ -0,0 +1,10 @@
+fn main() {
+    // On macOS, we need to link against the nginx object files
+    // because dynamic libraries can't have undefined symbols
+    #[cfg(target_os = "macos")]
+    {
+        println!("cargo:rustc-link-arg=-undefined");
+        println!("cargo:rustc-link-arg=dynamic_lookup");
+    }
+}
+