feat: enhance error handling with submission error overlay and logging level controls

css/main.css

@@ -1138,7 +1138,7 @@ select option:disabled {
     }
 }
 
-#submit-error-overlay, #view-answers-overlay {
+#view-answers-overlay {
     opacity: 0.9;
     position: absolute;
     top: 0;
@@ -1151,6 +1151,78 @@ select option:disabled {
     z-index: 5000;
 }
 
+#submit-error-overlay {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    background-color: rgba(0, 0, 0, 0.85);
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    z-index: 10000;
+    user-select: text;
+    -moz-user-select: text;
+    -webkit-user-select: text;
+    overflow-y: auto;
+    padding: 20px;
+    box-sizing: border-box;
+}
+
+#submit-error-overlay .error-card {
+    background-color: #1a1a1a;
+    border: 1px solid #c62828;
+    border-radius: 8px;
+    max-width: 600px;
+    width: 100%;
+    padding: 25px;
+    box-shadow: 0 10px 25px rgba(0,0,0,0.5);
+    color: #eee;
+    font-family: sans-serif;
+}
+
+#submit-error-overlay .error-card h3 {
+    margin-top: 0;
+    color: #ef5350;
+    font-size: 20px;
+    border-bottom: 1px solid #333;
+    padding-bottom: 10px;
+    margin-bottom: 15px;
+}
+
+#submit-error-overlay .error-card button {
+    cursor: pointer;
+    background-color: #311B92;
+    color: white;
+    border: none;
+    padding: 10px 18px;
+    font-size: 14px;
+    border-radius: 4px;
+    transition: background-color 0.2s;
+    font-weight: bold;
+}
+
+#submit-error-overlay .error-card button:hover {
+    background-color: #4527A0;
+}
+
+#submit-error-overlay .error-card button.btn-secondary {
+    background-color: #444;
+}
+
+#submit-error-overlay .error-card button.btn-secondary:hover {
+    background-color: #555;
+}
+
+#submit-error-overlay .error-card button.btn-danger {
+    background-color: #c62828;
+}
+
+#submit-error-overlay .error-card button.btn-danger:hover {
+    background-color: #d32f2f;
+}
+
 .cache-out-of-date {
     color: red;
 }