feat: JWT auth, /api prefix, SPA serving, OpenAPI, lean main.rs

- auth: register/login/refresh/logout w/ JWT+Argon2, protected mutations
- domain: User, RefreshSession, auth ports, Unauthorized/Forbidden errors
- presentation: context/state/factory/errors/extractors/openapi modules
- routes behind /api, SPA served from root w/ fallback
- OpenAPI Scalar at /docs
- frontend ssr:false, single-binary Dockerfile

crates/domain/Cargo.toml

@@ -8,3 +8,5 @@ thiserror = { workspace = true }
 uuid = { workspace = true }
 serde = { workspace = true }
 async-trait = { workspace = true }
+chrono = { version = "0.4", features = ["serde"] }
+email_address = "0.2"