fix(migration): guard 003 against pre-existing language column

alembic/versions/003_add_language_column.py

@@ -16,7 +16,18 @@ depends_on: Union[str, Sequence[str], None] = None
 
 
 def upgrade() -> None:
-    op.add_column("waitlist_entries", sa.Column("language", sa.String(5), nullable=False, server_default="en"))
+    # Guard: column may already exist from a prior manual migration
+    op.execute("""
+        DO $$
+        BEGIN
+            IF NOT EXISTS (
+                SELECT 1 FROM information_schema.columns
+                WHERE table_name = 'waitlist_entries' AND column_name = 'language'
+            ) THEN
+                ALTER TABLE waitlist_entries ADD COLUMN language VARCHAR(5) NOT NULL DEFAULT 'en';
+            END IF;
+        END $$;
+    """)
 
 
 def downgrade() -> None: