feat(scouts): add ScoutTriageQueue table + cloud_scout_configs gmail fields

Tasks 12+13 of Phase 2 — first new infra after rename.
Alembic 008 creates scout_triage_queue with unique constraint on
(scout_id, source_msg_ref) and partial index on expires_at for active
rows. Adds four columns to cloud_scout_configs: auto_trash_spam,
gmail_history_id, gmail_watch_expires_at, device_inactivity_pause_days.
SQLAlchemy model ScoutTriageQueue added; CloudScoutConfig updated to
match. Imports extended with UniqueConstraint and text.

alembic/versions/008_scout_triage_queue.py

@@ -0,0 +1,59 @@
+"""Scout triage queue + cloud_scout_configs alterations.
+
+Revision ID: 008
+Revises: 007
+Create Date: 2026-05-16
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+
+revision: str = "008"
+down_revision: Union[str, None] = "007"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "scout_triage_queue",
+        sa.Column("id", sa.Uuid(as_uuid=False), primary_key=True),
+        sa.Column("user_id", sa.Uuid(as_uuid=False), sa.ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True),
+        sa.Column("scout_id", sa.Uuid(as_uuid=False), sa.ForeignKey("cloud_scout_configs.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("source_type", sa.String(50), nullable=False),
+        sa.Column("source_msg_ref", sa.String(255), nullable=False),
+        sa.Column("triage_verdict", sa.String(20), nullable=False),
+        sa.Column("triage_reason", sa.Text, nullable=True),
+        sa.Column("status", sa.String(20), nullable=False, server_default="queued"),
+        sa.Column("triaged_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("delivered_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("acked_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=False),
+        sa.UniqueConstraint("scout_id", "source_msg_ref", name="uq_scout_triage_queue_scout_msg"),
+    )
+    op.create_index("ix_scout_triage_queue_user_status", "scout_triage_queue", ["user_id", "status"])
+    op.create_index(
+        "ix_scout_triage_queue_expires_active",
+        "scout_triage_queue",
+        ["expires_at"],
+        postgresql_where=sa.text("status != 'acked'"),
+    )
+
+    op.add_column("cloud_scout_configs", sa.Column("auto_trash_spam", sa.Boolean(), nullable=False, server_default=sa.text("false")))
+    op.add_column("cloud_scout_configs", sa.Column("gmail_history_id", sa.String(64), nullable=True))
+    op.add_column("cloud_scout_configs", sa.Column("gmail_watch_expires_at", sa.DateTime(timezone=True), nullable=True))
+    op.add_column("cloud_scout_configs", sa.Column("device_inactivity_pause_days", sa.Integer(), nullable=False, server_default="14"))
+
+
+def downgrade() -> None:
+    op.drop_column("cloud_scout_configs", "device_inactivity_pause_days")
+    op.drop_column("cloud_scout_configs", "gmail_watch_expires_at")
+    op.drop_column("cloud_scout_configs", "gmail_history_id")
+    op.drop_column("cloud_scout_configs", "auto_trash_spam")
+
+    op.drop_index("ix_scout_triage_queue_expires_active", table_name="scout_triage_queue")
+    op.drop_index("ix_scout_triage_queue_user_status", table_name="scout_triage_queue")
+    op.drop_table("scout_triage_queue")