feat: add DockingEvent model and docking styles

- Add DockingEvent model with parent/child asset relations, docked_at/undocked_at timestamps
- Add docking migration for new docking_events table
- Add .ad-dock, .ad-dock-box, .ad-dock-item, .ad-undock CSS classes

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

migrations/versions/2a4c9d8e7f10_add_docking_events.py

@@ -0,0 +1,46 @@
+"""add docking events
+
+Revision ID: 2a4c9d8e7f10
+Revises: 8bbf69ea2013
+Create Date: 2026-05-31 19:30:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "2a4c9d8e7f10"
+down_revision = "8bbf69ea2013"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        "docking_events",
+        sa.Column("id", sa.Uuid(), nullable=False),
+        sa.Column("parent_asset_id", sa.Uuid(), nullable=False),
+        sa.Column("child_asset_id", sa.Uuid(), nullable=True),
+        sa.Column("child_label", sa.String(length=255), nullable=True),
+        sa.Column("docked_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("undocked_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("dock_note", sa.Text(), nullable=True),
+        sa.Column("undock_note", sa.Text(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False),
+        sa.ForeignKeyConstraint(["child_asset_id"], ["assets.id"], ondelete="SET NULL"),
+        sa.ForeignKeyConstraint(["parent_asset_id"], ["assets.id"], ondelete="CASCADE"),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index(op.f("ix_docking_events_child_asset_id"), "docking_events", ["child_asset_id"], unique=False)
+    op.create_index(op.f("ix_docking_events_docked_at"), "docking_events", ["docked_at"], unique=False)
+    op.create_index(op.f("ix_docking_events_parent_asset_id"), "docking_events", ["parent_asset_id"], unique=False)
+    op.create_index(op.f("ix_docking_events_undocked_at"), "docking_events", ["undocked_at"], unique=False)
+
+
+def downgrade():
+    op.drop_index(op.f("ix_docking_events_undocked_at"), table_name="docking_events")
+    op.drop_index(op.f("ix_docking_events_parent_asset_id"), table_name="docking_events")
+    op.drop_index(op.f("ix_docking_events_docked_at"), table_name="docking_events")
+    op.drop_index(op.f("ix_docking_events_child_asset_id"), table_name="docking_events")
+    op.drop_table("docking_events")