feat: Enhance goodbye and welcome forms with new message types and image options

- Added support for different message types (text, embed, both) in goodbye and welcome forms.
- Implemented embed options including title, description, color, thumbnail, and footer for both forms.
- Introduced image options with gradient selection, title, subtitle, and member count display for goodbye and welcome messages.
- Updated API routes to handle new configuration parameters for saving and retrieving goodbye and welcome settings.
- Created a new function to generate welcome images with customizable gradients and text.

app/public/guild.css

@@ -1528,3 +1528,81 @@ body {
   padding: var(--spacing-lg);
 }
 
+/* ===== Gradient Picker ===== */
+.gradient-picker {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--spacing-sm);
+  margin-top: var(--spacing-xs);
+}
+
+.gradient-option {
+  width: 50px;
+  height: 50px;
+  border-radius: var(--radius-md);
+  cursor: pointer;
+  border: 3px solid transparent;
+  transition: all 0.2s ease;
+  position: relative;
+}
+
+.gradient-option:hover {
+  transform: scale(1.1);
+  box-shadow: var(--shadow-md);
+}
+
+.gradient-option.selected {
+  border-color: var(--primary);
+  box-shadow: 0 0 0 2px var(--primary), var(--shadow-md);
+}
+
+.gradient-option.selected::after {
+  content: '✓';
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  color: white;
+  font-size: 1.2rem;
+  font-weight: bold;
+  text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
+}
+
+/* ===== Image Preview ===== */
+.image-preview {
+  background: var(--bg-secondary);
+  border: 1px solid var(--border-color);
+  border-radius: var(--radius-md);
+  min-height: 150px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  overflow: hidden;
+}
+
+.image-preview img {
+  max-width: 100%;
+  height: auto;
+  border-radius: var(--radius-sm);
+}
+
+.preview-placeholder {
+  color: var(--text-muted);
+  font-style: italic;
+}
+
+/* ===== Color Input ===== */
+.form-color {
+  height: 45px;
+  padding: 5px;
+  cursor: pointer;
+}
+
+.form-color::-webkit-color-swatch-wrapper {
+  padding: 2px;
+}
+
+.form-color::-webkit-color-swatch {
+  border: none;
+  border-radius: var(--radius-sm);
+}