feat: add Alembic database migrations

- alembic.ini: Alembic configuration
- alembic/env.py: migration environment with Base import
- alembic/versions/001_initial_schema.py: initial schema migration (projects, asset_libraries, assets, ingest_jobs)
- alembic/README.md: migration usage guide
- all 7 integration tests still passing

alembic.ini

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+# Alembic Config file
+
+[alembic]
+script_location = alembic
+prepend_sys_path = .
+sqlalchemy.url = postgresql://postgres:postgres@localhost:5432/xiaoxia_saas
+
+[post_write_hooks]
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

alembic/README.md

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+# Alembic Migrations
+
+This directory contains database migration scripts managed by Alembic.
+
+## Usage
+
+```bash
+# Apply all pending migrations
+alembic upgrade head
+
+# Rollback one migration
+alembic downgrade -1
+
+# Show current revision
+alembic current
+
+# Show migration history
+alembic history
+```
+
+## Current Migrations
+
+- `001_initial_schema.py` - Initial database schema (projects, asset_libraries, assets, ingest_jobs)

alembic/env.py

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+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Import your models' Base here
+from packages.adapters.sqlalchemy_impl.models import Base
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    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 run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    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()

alembic/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

alembic/versions/001_initial_schema.py

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+"""Initial schema
+
+Revision ID: 001
+Revises: 
+Create Date: 2026-06-15
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '001'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Create projects table
+    op.create_table(
+        'projects',
+        sa.Column('id', sa.String(32), nullable=False),
+        sa.Column('workspace_id', sa.String(32), nullable=False),
+        sa.Column('name', sa.String(100), nullable=False),
+        sa.Column('description', sa.Text(), nullable=False, server_default=''),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_projects_workspace_id'), 'projects', ['workspace_id'], unique=False)
+
+    # Create asset_libraries table
+    op.create_table(
+        'asset_libraries',
+        sa.Column('id', sa.String(32), nullable=False),
+        sa.Column('workspace_id', sa.String(32), nullable=False),
+        sa.Column('project_id', sa.String(32), nullable=False),
+        sa.Column('name', sa.String(100), nullable=False),
+        sa.Column('kind', sa.String(20), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_asset_libraries_workspace_id'), 'asset_libraries', ['workspace_id'], unique=False)
+    op.create_index(op.f('ix_asset_libraries_project_id'), 'asset_libraries', ['project_id'], unique=False)
+
+    # Create assets table
+    op.create_table(
+        'assets',
+        sa.Column('id', sa.String(32), nullable=False),
+        sa.Column('workspace_id', sa.String(32), nullable=False),
+        sa.Column('project_id', sa.String(32), nullable=False),
+        sa.Column('library_id', sa.String(32), nullable=False),
+        sa.Column('name', sa.String(100), nullable=False),
+        sa.Column('storage_key', sa.String(255), nullable=False),
+        sa.Column('mime_type', sa.String(100), nullable=False),
+        sa.Column('metadata_json', sa.Text(), nullable=False, server_default='{}'),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_assets_workspace_id'), 'assets', ['workspace_id'], unique=False)
+    op.create_index(op.f('ix_assets_project_id'), 'assets', ['project_id'], unique=False)
+    op.create_index(op.f('ix_assets_library_id'), 'assets', ['library_id'], unique=False)
+
+    # Create ingest_jobs table
+    op.create_table(
+        'ingest_jobs',
+        sa.Column('id', sa.String(32), nullable=False),
+        sa.Column('workspace_id', sa.String(32), nullable=False),
+        sa.Column('project_id', sa.String(32), nullable=False),
+        sa.Column('library_id', sa.String(32), nullable=False),
+        sa.Column('storage_key', sa.String(255), nullable=False),
+        sa.Column('status', sa.String(20), nullable=False, server_default='pending'),
+        sa.Column('error_message', sa.Text(), nullable=False, server_default=''),
+        sa.Column('result_asset_id', sa.String(32), nullable=False, server_default=''),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_ingest_jobs_workspace_id'), 'ingest_jobs', ['workspace_id'], unique=False)
+    op.create_index(op.f('ix_ingest_jobs_project_id'), 'ingest_jobs', ['project_id'], unique=False)
+    op.create_index(op.f('ix_ingest_jobs_library_id'), 'ingest_jobs', ['library_id'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_table('ingest_jobs')
+    op.drop_table('assets')
+    op.drop_table('asset_libraries')
+    op.drop_table('projects')