Fix ngx 0.5.0 API compatibility

- Update HttpModule trait implementation to match ngx 0.5.0 API
- Implement HttpModuleLocationConf as separate unsafe trait
- Fix configuration access using Module::location_conf()
- Replace ngx_null_command macro with explicit null command
- Update imports to use correct constant names
- Suppress C FFI naming convention warnings

.envrc

@@ -1,5 +1,7 @@
 use flake
 unset TMPDIR
-export NGINX_SOURCE_DIR=$PWD/ngx_src/nginx-1.28.0
+export NGINX_SOURCE_DIR=$PWD/ngx_src/nginx-1.28.0/
+export NGINX_BUILD_DIR=$PWD/ngx_src/nginx-1.28.0/objs/
 export ZLIB_VERSION=1.3.1
+export NGX_VERSION=1.28.0
 export CFLAGS='-Wno-unterminated-string-initialization'