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.

apps/agent/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "yanpm-agent"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+axum = { version = "0.8.7", features = ["form", "http1", "json", "matched-path", "original-uri", "query", "tokio", "tower-log", "tracing", "macros"] }
+tokio = { version = "1", features = ["fs", "io-util", "io-std", "macros", "net", "parking_lot", "process", "rt", "rt-multi-thread", "signal", "sync", "time", "tracing"] }
+tracing = { version = "0.1.41", features = ["std", "attributes"] }
+tracing-subscriber = { version = "0.3.20", features = ["smallvec", "fmt", "ansi", "tracing-log", "std", "json", "serde", "serde_json", "time", "tracing"] }
+serde_json = { version = "1.0.145", features = ["std"] }
+serde = { version = "1.0.228", features = ["std", "derive"] }
+tokio-cron-scheduler = { version = "0.15.1", features = ["signal"] }
+clap = { version = "4", features = ["derive"] }