chore(infra): add gRPC layer, update protobufs, remove immediate module

- Add gRPC service modules: auth, channel, channel settings, member,
  permission
- Update protobuf definitions and generated code
- Remove immediate/ real-time module (superseded by IM service)
- Update etcd discovery and registration
- Update cache, error, config, and build infrastructure
- Add ADR documentation
- Update OpenAPI spec

gen_openapi.rs

@@ -2,10 +2,13 @@ use appks::api::openapi::OpenApiDoc;
 use utoipa::OpenApi;
 
 fn main() {
+    println!("Generating OpenAPI documentation...");
     let json = OpenApiDoc::openapi().to_pretty_json();
     if let Ok(json) = json {
         if let Err(e) = std::fs::write("openapi.json", json) {
-            eprintln!("{}", e);
+            println!("Failed to write OpenAPI documentation. {}", e);
+        } else {
+            println!("OpenAPI documentation generated successfully.");
         }
     }
 }