feat: add featured event with automatic fallback

- Add featured_event_id to site_settings (schema + migration)
- Backend: featured event logic in /events/next/upcoming with auto-unset when event ends
- Site settings: PUT supports featuredEventId, add PUT /featured-event for admin
- Admin events: Set as featured checkbox in editor, star toggle in list, featured badge
- Admin settings: Featured Event section with current event and remove/change links
- API: siteSettingsApi.setFeaturedEvent(), Event.isFeatured, SiteSettings.featuredEventId
- Homepage/linktree unchanged: still use getNextUpcoming (now returns featured or fallback)

backend/src/db/migrate.ts

@@ -388,6 +388,7 @@ async function migrate() {
         instagram_url TEXT,
         twitter_url TEXT,
         linkedin_url TEXT,
+        featured_event_id TEXT REFERENCES events(id),
         maintenance_mode INTEGER NOT NULL DEFAULT 0,
         maintenance_message TEXT,
         maintenance_message_es TEXT,
@@ -396,6 +397,11 @@ async function migrate() {
       )
     `);
 
+    // Add featured_event_id column to site_settings if it doesn't exist
+    try {
+      await (db as any).run(sql`ALTER TABLE site_settings ADD COLUMN featured_event_id TEXT REFERENCES events(id)`);
+    } catch (e) { /* column may already exist */ }
+
     // Legal pages table for admin-editable legal content
     await (db as any).run(sql`
       CREATE TABLE IF NOT EXISTS legal_pages (
@@ -748,6 +754,7 @@ async function migrate() {
         instagram_url VARCHAR(500),
         twitter_url VARCHAR(500),
         linkedin_url VARCHAR(500),
+        featured_event_id UUID REFERENCES events(id),
         maintenance_mode INTEGER NOT NULL DEFAULT 0,
         maintenance_message TEXT,
         maintenance_message_es TEXT,
@@ -756,6 +763,11 @@ async function migrate() {
       )
     `);
 
+    // Add featured_event_id column to site_settings if it doesn't exist
+    try {
+      await (db as any).execute(sql`ALTER TABLE site_settings ADD COLUMN featured_event_id UUID REFERENCES events(id)`);
+    } catch (e) { /* column may already exist */ }
+
     // Legal pages table for admin-editable legal content
     await (db as any).execute(sql`
       CREATE TABLE IF NOT EXISTS legal_pages (