feat: add documentation crate and integrate OpenAPI specifications

- Added a new crate `doc` for API documentation.
- Integrated `utoipa` for OpenAPI support in the presentation layer.
- Updated routes to include social features (follow, unfollow, etc.) and diary export.
- Enhanced API request and response structures with new DTOs for social interactions.
- Updated `Cargo.toml` files to include new dependencies and features.
- Modified Dockerfile to copy the new documentation crate.
- Refactored existing handlers and routes to accommodate new API endpoints.
- Updated tests to cover new functionality and ensure proper API behavior.

crates/doc/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "doc"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+axum = { workspace = true }
+tracing = { workspace = true }
+utoipa = { version = "5.5.0", features = ["axum_extras"] }
+utoipa-scalar = { version = "0.3.0", features = [
+    "axum",
+], default-features = false }
+utoipa-swagger-ui = { version = "9.0.2", features = ["axum", "vendored"] }