fix: add storage deletion with library cleanup and scan validation

- Delete storage config now properly removes related libraries and media
- Scanner validates storage config exists before starting cloud scan
- Prevents orphaned scans when storage is removed
- Added repository methods: DeleteByType, FindByID for storage config
- Remove unused storageHandler route to fix compilation

internal/handler/storage.go

@@ -1,21 +0,0 @@
-// Package handler — disk usage breakdown for the Storage tab.
-package handler
-
-import (
-	"net/http"
-
-	"github.com/gin-gonic/gin"
-
-	"github.com/ShukeBta/MediaStationGo/internal/service"
-)
-
-func storageHandler(svc *service.Container) gin.HandlerFunc {
-	return func(c *gin.Context) {
-		bd, err := svc.Storage.Compute(c.Request.Context())
-		if err != nil {
-			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
-			return
-		}
-		c.JSON(http.StatusOK, bd)
-	}
-}