Download REST API endpoints (#72)

* backend and frontend hotfixes, see message

Improved rendering on the frontend by cutting unecessary useStates.
Backend side, downloads now auto resume even on application kill.

* download rest api endpoints, general code refactor

* download request json mappings

server/rest/provider.go

@@ -0,0 +1,34 @@
+package rest
+
+import (
+	"sync"
+
+	"github.com/marcopeocchi/yt-dlp-web-ui/server/internal"
+)
+
+var (
+	service *Service
+	handler *Handler
+
+	serviceOnce sync.Once
+	handlerOnce sync.Once
+)
+
+func ProvideService(db *internal.MemoryDB, mq *internal.MessageQueue) *Service {
+	serviceOnce.Do(func() {
+		service = &Service{
+			db: db,
+			mq: mq,
+		}
+	})
+	return service
+}
+
+func ProvideHandler(svc *Service) *Handler {
+	handlerOnce.Do(func() {
+		handler = &Handler{
+			service: svc,
+		}
+	})
+	return handler
+}