feat: add OpenAPI spec generation with utoipa and justfile

- Add utoipa v5 dependency with ToSchema derives on all REST API DTOs
- Annotate free-function handlers with #[utoipa::path] (trash, share, favorites, recent)
- Create ApiDoc struct with OpenApi derive registering 37 schemas across 7 tags
- Add generate-openapi binary outputting resources/gen/openapi.json
- Serve OpenAPI spec at GET /api/openapi.json (public, no auth)
- Add justfile with common dev commands (build, test, lint, check, openapi, db)

src/interfaces/api/routes.rs

@@ -9,8 +9,8 @@ use axum::{
 use serde_json::json;
 use std::sync::Arc;
 use tower_http::{compression::CompressionLayer, trace::TraceLayer};
+use utoipa::OpenApi;
 
-/// Returns the application version from Cargo.toml (compile-time constant)
 async fn get_version() -> AxumJson<serde_json::Value> {
     AxumJson(json!({
         "name": "OxiCloud",
@@ -18,6 +18,10 @@ async fn get_version() -> AxumJson<serde_json::Value> {
     }))
 }
 
+async fn get_openapi_spec() -> AxumJson<utoipa::openapi::OpenApi> {
+    AxumJson(super::ApiDoc::openapi())
+}
+
 use crate::interfaces::api::handlers::admin_handler;
 use crate::interfaces::api::handlers::batch_handler::{self, BatchHandlerState};
 use crate::interfaces::api::handlers::chunked_upload_handler::ChunkedUploadHandler;
@@ -64,6 +68,7 @@ pub fn create_public_api_routes(app_state: &Arc<AppState>) -> Router<Arc<AppStat
 
     // Version endpoint — public, no auth required
     router = router.route("/version", get(get_version));
+    router = router.route("/openapi.json", get(get_openapi_spec));
 
     router
 }