Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/alembic/env.py

@@ -0,0 +1,81 @@
+import asyncio
+from logging.config import fileConfig
+
+from sqlalchemy import pool
+from sqlalchemy.engine import Connection
+from sqlalchemy.ext.asyncio import async_engine_from_config
+
+from alembic import context
+
+# Import your models
+from app.core.database import Base
+from app.models import User, Team, Tree, Session, Attachment
+from app.core.config import settings
+
+# this is the Alembic Config object
+config = context.config
+
+# Override sqlalchemy.url with the sync version for migrations
+config.set_main_option("sqlalchemy.url", settings.DATABASE_URL_SYNC)
+
+# Interpret the config file for Python logging.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode."""
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection: Connection) -> None:
+    context.configure(connection=connection, target_metadata=target_metadata)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    """Run migrations in 'online' mode with async engine."""
+    from sqlalchemy.ext.asyncio import create_async_engine
+
+    connectable = create_async_engine(
+        settings.DATABASE_URL,
+        poolclass=pool.NullPool,
+    )
+
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+    from sqlalchemy import create_engine
+
+    connectable = create_engine(
+        settings.DATABASE_URL_SYNC,
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        do_run_migrations(connection)
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()