feat: Add banner management feature and improve event/gallery image handling

- Introduced a new "Banners" feature, enabling banner creation, management, and display across the admin panel and frontend.
- Enhanced image handling for events and gallery by converting images to optimized webp format.
- Added `banners` table in the database schema for storing announcements.
- Integrated new `/api/banners` route in backend for banner operations.
- Updated `index.astro` to include banner display component.
- Added supporting UI and APIs in the admin panel for banner management.

backend/src/db/schema.ts

@@ -60,3 +60,14 @@ export const publishHistory = sqliteTable('publish_history', {
   commitMessage: text('commit_message'),
   publishedAt: integer('published_at', { mode: 'timestamp' }).default(sql`(unixepoch())`),
 });
+
+// Banner table (for announcements like holidays, special info)
+export const banners = sqliteTable('banners', {
+  id: text('id').primaryKey().$defaultFn(() => crypto.randomUUID()),
+  text: text('text').notNull(),
+  startDate: text('start_date').notNull(), // ISO date string
+  endDate: text('end_date').notNull(), // ISO date string
+  isActive: integer('is_active', { mode: 'boolean' }).default(true),
+  createdAt: integer('created_at', { mode: 'timestamp' }).default(sql`(unixepoch())`),
+  updatedAt: integer('updated_at', { mode: 'timestamp' }).default(sql`(unixepoch())`),
+});