build share count

backend/src/db.ts

@@ -66,6 +66,10 @@ if (!memesCols.find((c) => c.name === 'ocr_text')) {
   db.exec('ALTER TABLE memes ADD COLUMN ocr_text TEXT');
 }
 
+if (!memesCols.find((c) => c.name === 'share_count')) {
+  db.exec('ALTER TABLE memes ADD COLUMN share_count INTEGER NOT NULL DEFAULT 0');
+}
+
 // Indexes that depend on migrated columns — created after columns are guaranteed to exist
 db.exec(`
   CREATE INDEX IF NOT EXISTS idx_memes_collection_id ON memes(collection_id);