feat: add agent module with Nginx service commands and routes

- Introduced a new agent module with commands for managing Nginx configurations.
- Implemented `NginxService` for handling reload, validation, and configuration writing.
- Added routes for status, validation, and configuration writing using Axum.
- Created necessary command files: `reload.rs`, `run.rs`, `validate.rs`, `write_config.rs`.
- Updated `Cargo.toml` and `Cargo.lock` to include new dependencies.
- Added `.gitignore` for the agent module.
- Updated `justfile` to include OpenAPI generation for the agent.

Cargo.toml

@@ -1,8 +1,9 @@
 [workspace]
-members = [ 
+members = [
     "apps/api",
     "apps/container",
     "apps/cli",
+    "apps/agent",
     "public/shared",
     "public/database",
     "public/migration"