feat: add event watcher

backend/migrations/versions/a3f1c8e94d72_phase10_1_alert_dedup_key.py

@@ -0,0 +1,33 @@
+"""phase10.1 alert dedup key
+
+Revision ID: a3f1c8e94d72
+Revises: 6b2d95ac3b46
+Create Date: 2026-05-30 02:00:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "a3f1c8e94d72"
+down_revision: str | None = "6b2d95ac3b46"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    op.add_column("alerts", sa.Column("dedup_key", sa.Text(), nullable=True))
+    op.create_index(
+        "ix_alerts_watch_dedup",
+        "alerts",
+        ["watch_id", "dedup_key"],
+        unique=True,
+        postgresql_where=sa.text("dedup_key IS NOT NULL"),
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_alerts_watch_dedup", table_name="alerts")
+    op.drop_column("alerts", "dedup_key")