Fix Docker build: include drizzle/ migrations in build context

drizzle/ was excluded in .dockerignore but the Dockerfile copies it into
the runner stage (needed by migrate.mjs at container startup). Remove the
exclusion so migration SQL files are present in the builder stage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.dockerignore

@@ -2,7 +2,6 @@ node_modules
 .next
 .git
 deploy
-drizzle
 docs
 *.md
 .env*