feat(core): add alembic migration for attachments table

alembic/versions/0011_attachments.py

@@ -0,0 +1,44 @@
+"""Create attachments table.
+
+Revision ID: 0011_attachments
+Revises: 0010_system_settings
+Create Date: 2026-07-04
+"""
+
+from __future__ import annotations
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision: str = "0011_attachments"
+down_revision: Union[str, None] = "0010_system_settings"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "attachments",
+        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
+        sa.Column("entity_type", sa.String(50), nullable=False),
+        sa.Column("entity_id", postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column("filename", sa.String(255), nullable=False),
+        sa.Column("file_path", sa.String(500), nullable=False),
+        sa.Column("mime_type", sa.String(100), nullable=False, server_default="application/octet-stream"),
+        sa.Column("file_size", sa.Integer, nullable=False, server_default="0"),
+        sa.Column("uploaded_by", postgresql.UUID(as_uuid=True),
+                  sa.ForeignKey("users.id", ondelete="SET NULL"), nullable=True),
+        sa.Column("tenant_id", postgresql.UUID(as_uuid=True), nullable=False, index=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
+    )
+    op.create_index("ix_attachments_entity", "attachments", ["entity_type", "entity_id", "tenant_id"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_attachments_entity", table_name="attachments")
+    op.drop_table("attachments")