feat(api,userbot,frontend): add accounts from the web ui and isolate per-account settings

backend/migrations/versions/e7b4c2a9f861_per_account_policy_defaults.py

@@ -0,0 +1,43 @@
+"""per-account policy defaults
+
+Revision ID: e7b4c2a9f861
+Revises: d5f9b2c8e3a1
+Create Date: 2026-08-05 23:10:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+revision: str = "e7b4c2a9f861"
+down_revision: str | None = "d5f9b2c8e3a1"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+_SCOPE_KEY = "capture_policy_account_id_scope_type_scope_id_key"
+
+
+def upgrade() -> None:
+    op.execute("DROP INDEX ix_capture_policy_default")
+    op.execute(f"ALTER TABLE capture_policy DROP CONSTRAINT {_SCOPE_KEY}")
+    op.execute(
+        "CREATE UNIQUE INDEX ix_capture_policy_scope ON capture_policy "
+        "(account_id, scope_type, scope_id) NULLS NOT DISTINCT"
+    )
+
+
+def downgrade() -> None:
+    op.execute(
+        "DELETE FROM capture_policy WHERE account_id IS NOT NULL "
+        "AND scope_type LIKE 'default_%'"
+    )
+    op.execute("DROP INDEX ix_capture_policy_scope")
+    op.execute(
+        f"ALTER TABLE capture_policy ADD CONSTRAINT {_SCOPE_KEY} "
+        "UNIQUE (account_id, scope_type, scope_id)"
+    )
+    op.execute(
+        "CREATE UNIQUE INDEX ix_capture_policy_default "
+        "ON capture_policy (scope_type) WHERE scope_type LIKE 'default_%'"
+    )