Show loading spinners for form actions and page loads

web-app/src/lib/components/LoadingSpinner.svelte

@@ -0,0 +1,32 @@
+<div class="spinner"></div>
+
+<style>
+  @keyframes spinner {
+    to {
+      transform: rotate(360deg);
+    }
+  }
+
+  .spinner {
+    position: fixed;
+    inset: 0;
+    background-color: rgba(0, 0, 0, 0.5);
+    z-index: 40;
+  }
+
+  .spinner::before {
+    content: "";
+    position: absolute;
+    inline-size: 4rem;
+    block-size: 4rem;
+    inset-block-start: 50%;
+    inset-inline-start: 50%;
+    margin-block-start: -2rem;
+    margin-inline-start: -2rem;
+    border-radius: 50%;
+    border: var(--border-primary);
+    border-width: 0.125rem;
+    border-block-start-color: var(--color-accent);
+    animation: spinner 0.6s linear infinite;
+  }
+</style>