feat(db): add DeckyLifecycle table for async deploy/mutate tracking

One row per (decky, operation) attempt. State machine:
pending -> running -> succeeded | failed (+ error text). Rows are
append-only after terminal; retries write a new row.

Sibling of DeckyShard rather than a rework -- DeckyShard tracks
runtime container state observed via heartbeat, this tracks
operation lifecycle. New table, UUID PK.

Adds BaseRepository abstract methods (create_lifecycle,
update_lifecycle, get_lifecycle_by_ids, find_open_lifecycle,
sweep_stale_lifecycle) with SQLModelRepository mixin impl.
Backbone for the upcoming 202-Accepted async API.

decnet/web/db/sqlmodel_repo/__init__.py

@@ -42,6 +42,7 @@ from decnet.web.db.sqlmodel_repo.campaigns import CampaignsMixin
 from decnet.web.db.sqlmodel_repo.canary import CanaryMixin
 from decnet.web.db.sqlmodel_repo.credentials import CredentialsMixin
 from decnet.web.db.sqlmodel_repo.deckies import DeckiesMixin
+from decnet.web.db.sqlmodel_repo.decky_lifecycle import LifecycleMixin
 from decnet.web.db.sqlmodel_repo.fleet import FleetMixin
 from decnet.web.db.sqlmodel_repo.identities import IdentitiesMixin
 from decnet.web.db.sqlmodel_repo.logs import LogsMixin
@@ -66,6 +67,7 @@ class SQLModelRepository(
     CanaryMixin,
     CredentialsMixin,
     DeckiesMixin,
+    LifecycleMixin,
     FleetMixin,
     IdentitiesMixin,
     LogsMixin,