feat: add Alembic migration with schema and seed data

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

backend/alembic/env.py

@@ -0,0 +1,42 @@
+import os
+from logging.config import fileConfig
+from sqlalchemy import engine_from_config, pool
+from alembic import context
+
+config = context.config
+
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# Override sqlalchemy.url from environment
+database_url = os.environ.get("DATABASE_URL")
+if database_url:
+    config.set_main_option("sqlalchemy.url", database_url)
+
+from app.models import Base  # noqa: E402
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(url=url, target_metadata=target_metadata, literal_binds=True)
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    with connectable.connect() as connection:
+        context.configure(connection=connection, target_metadata=target_metadata)
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()