ui: Display a spinner during gradation launch

ui/src/routes/works/[wid]/rendus/+page.svelte

@@ -32,16 +32,21 @@
      repositoriesP[userid] = getRepositories(wid, userid);
  }
 
+ let gradation_preflight = false;
  async function runGradations() {
+     gradation_preflight = true;
      for (const user of await usersP) {
          if (repositoriesP[user.id]) {
              try {
                  for (const repo of await repositoriesP[user.id]) {
                      repo.runGradation();
                  }
-             } catch {}
+             } catch (err) {
+                 ToastsStore.addToast({color: "danger", title: "Impossible de lancer la notation de " + user.login, msg: err})
+             }
          }
      }
+     gradation_preflight = false;
 }
 
  let nb_rendus = 0;
@@ -66,8 +71,13 @@
             class="btn btn-sm btn-success mr-1"
             title="Relancer les tests"
             on:click={runGradations}
+            disabled={gradation_preflight}
         >
-            <i class="bi bi-play"></i>
+            {#if gradation_preflight}
+                <div class="spinner-border spinner-border-sm" role="status"></div>
+            {:else}
+                <i class="bi bi-play"></i>
+            {/if}
         </button>
     </div>
 </div>