feat(automation): add SQLAlchemy models for the three v1 tables

Three enums (one file each) plus three models (one file each), all
under app/automations/persistence/. The module imports from app.db
only (Base/BaseModel/TimestampMixin and FK targets searchspaces.id /
user.id); no business-logic imports.

Enums:
  - AutomationStatus: active | paused | archived
  - RunStatus: pending | running | succeeded | failed | cancelled
    | timed_out
  - TriggerType: schedule | manual (Phase-2/3 add webhook | event)

Models:
  - Automation: search_space-scoped, created_by_user_id (SET NULL),
    name + description, status enum, definition JSONB, version int,
    updated_at with onupdate.
  - AutomationTrigger: FK → automations (CASCADE), type enum, config
    JSONB, enabled bool, last_fired_at. Webhook secret_hash is omitted
    until Phase 2.
  - AutomationRun: FK → automations (CASCADE), nullable trigger_id
    (SET NULL — null = manual via UI), status enum,
    definition_snapshot for immutable history, trigger_payload /
    resolved_inputs / step_results / output / artifacts / error JSONB
    columns, started_at / finished_at timestamps, agent_session_id for
    linking to the LangGraph trace. cost_usd column omitted until at
    least one v1 capability records token-level cost.

Verified: Base.metadata exposes all three table names; columns and
enums introspect as documented; no linter errors.

surfsense_backend/app/automations/persistence/models/automation.py

@@ -0,0 +1,75 @@
+"""``Automation`` table — the editable, versioned automation definition."""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime
+
+from sqlalchemy import (
+    TIMESTAMP,
+    Column,
+    Enum as SQLAlchemyEnum,
+    ForeignKey,
+    Integer,
+    String,
+    Text,
+)
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+
+from app.db import BaseModel, TimestampMixin
+
+from ..enums.automation_status import AutomationStatus
+
+
+class Automation(BaseModel, TimestampMixin):
+    """The editable, versioned spec a user authors.
+
+    The ``definition`` JSON is what the user (or the NL generator) writes
+    and edits. Each save bumps ``version`` by one; the previous JSON is
+    not kept in this row — version history is reconstructed from the
+    ``definition_snapshot`` column on every ``AutomationRun`` that fired
+    against a given version.
+    """
+
+    __tablename__ = "automations"
+
+    search_space_id = Column(
+        Integer,
+        ForeignKey("searchspaces.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+
+    created_by_user_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("user.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
+
+    name = Column(String(200), nullable=False)
+    description = Column(Text, nullable=True)
+
+    status = Column(
+        SQLAlchemyEnum(AutomationStatus, name="automation_status"),
+        nullable=False,
+        default=AutomationStatus.ACTIVE,
+        server_default=AutomationStatus.ACTIVE.value,
+        index=True,
+    )
+
+    definition = Column(JSONB, nullable=False)
+
+    version = Column(
+        Integer,
+        nullable=False,
+        default=1,
+        server_default="1",
+    )
+
+    updated_at = Column(
+        TIMESTAMP(timezone=True),
+        nullable=False,
+        default=lambda: datetime.now(UTC),
+        onupdate=lambda: datetime.now(UTC),
+        index=True,
+    )