Deliver per (inbox, domain) — federation actor gets all posts too

Add app_domain to APDeliveryLog so the same activity can be delivered
to the same inbox under different actor identities (blog + federation).

alembic/versions/u1s9o5p7q8_add_app_domain_to_delivery_log.py

@@ -0,0 +1,33 @@
+"""Add app_domain to ap_delivery_log for per-domain idempotency
+
+Revision ID: u1s9o5p7q8
+Revises: t0r8n4o6p7
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "u1s9o5p7q8"
+down_revision = "t0r8n4o6p7"
+
+
+def upgrade() -> None:
+    op.add_column(
+        "ap_delivery_log",
+        sa.Column("app_domain", sa.String(128), nullable=False, server_default="federation"),
+    )
+    op.drop_constraint("uq_delivery_activity_inbox", "ap_delivery_log", type_="unique")
+    op.create_unique_constraint(
+        "uq_delivery_activity_inbox_domain",
+        "ap_delivery_log",
+        ["activity_id", "inbox_url", "app_domain"],
+    )
+
+
+def downgrade() -> None:
+    op.drop_constraint("uq_delivery_activity_inbox_domain", "ap_delivery_log", type_="unique")
+    op.drop_column("ap_delivery_log", "app_domain")
+    op.create_unique_constraint(
+        "uq_delivery_activity_inbox",
+        "ap_delivery_log",
+        ["activity_id", "inbox_url"],
+    )