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/handlers/file_handler.rs

@@ -9,6 +9,7 @@ use bytes::Bytes;
 use http_range_header::parse_range_header;
 use serde::Deserialize;
 use std::collections::HashMap;
+use utoipa::ToSchema;
 
 use crate::application::ports::file_ports::OptimizedFileContent;
 use crate::application::ports::file_ports::{
@@ -1005,7 +1006,7 @@ impl FileHandler {
 }
 
 /// Payload for moving a file
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, ToSchema)]
 pub struct MoveFilePayload {
     /// Target folder ID (None means root)
     pub folder_id: Option<String>,