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/application/dtos/trash_dto.rs

@@ -1,8 +1,9 @@
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
+use utoipa::ToSchema;
 
 /// DTO representing an item in the trash
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Serialize, Deserialize, ToSchema)]
 pub struct TrashedItemDto {
     pub id: String,
     pub original_id: String,
@@ -20,20 +21,20 @@ pub struct TrashedItemDto {
 }
 
 /// Request to move an item to trash
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, ToSchema)]
 pub struct MoveToTrashRequest {
     pub item_id: String,
     pub item_type: String, // "file" o "folder"
 }
 
 /// Request to restore an item from trash
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, ToSchema)]
 pub struct RestoreFromTrashRequest {
     pub trash_id: String,
 }
 
 /// Request to permanently delete an item from trash
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, ToSchema)]
 pub struct DeletePermanentlyRequest {
     pub trash_id: String,
 }