feat: document user management system and RBAC implementation

- Update copilot-instructions.md with user model, API routes, and frontend patterns
- Update README.md with RBAC details, user management API, and security sections
- Add user management technical documentation to TECH-CHANGELOG.md
- Bump version to 2025.1.0-alpha.13 with user management changelog entries

server/alembic/versions/4f0b8a3e5c20_add_user_audit_fields.py

@@ -0,0 +1,52 @@
+"""add user audit fields
+
+Revision ID: 4f0b8a3e5c20
+Revises: 21226a449037
+Create Date: 2025-12-29 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = '4f0b8a3e5c20'
+down_revision: Union[str, None] = '21226a449037'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    op.add_column('users', sa.Column('last_login_at', sa.TIMESTAMP(timezone=True), nullable=True))
+    op.add_column('users', sa.Column('last_password_change_at', sa.TIMESTAMP(timezone=True), nullable=True))
+    op.add_column('users', sa.Column('last_failed_login_at', sa.TIMESTAMP(timezone=True), nullable=True))
+    op.add_column(
+        'users',
+        sa.Column('failed_login_attempts', sa.Integer(), nullable=False, server_default='0')
+    )
+    op.add_column('users', sa.Column('locked_until', sa.TIMESTAMP(timezone=True), nullable=True))
+    op.add_column('users', sa.Column('deactivated_at', sa.TIMESTAMP(timezone=True), nullable=True))
+    op.add_column('users', sa.Column('deactivated_by', sa.Integer(), nullable=True))
+    op.create_foreign_key(
+        'fk_users_deactivated_by_users',
+        'users',
+        'users',
+        ['deactivated_by'],
+        ['id'],
+        ondelete='SET NULL',
+    )
+    # Optional: keep server_default for failed_login_attempts; remove if you prefer no default after backfill
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    op.drop_constraint('fk_users_deactivated_by_users', 'users', type_='foreignkey')
+    op.drop_column('users', 'deactivated_by')
+    op.drop_column('users', 'deactivated_at')
+    op.drop_column('users', 'locked_until')
+    op.drop_column('users', 'failed_login_attempts')
+    op.drop_column('users', 'last_failed_login_at')
+    op.drop_column('users', 'last_password_change_at')
+    op.drop_column('users', 'last_login_at')