feat: The Other Dude v9.0.1 — full-featured email system

ci: add GitHub Pages deployment workflow for docs site

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/alembic/versions/023_slack_notification_channel.py

@@ -0,0 +1,21 @@
+"""Add Slack notification channel support.
+
+Revision ID: 023
+Revises: 022
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+revision = "023"
+down_revision = "022"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("notification_channels", sa.Column("slack_webhook_url", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("notification_channels", "slack_webhook_url")