feat(dashboard): orchestration canvas fase 2 — History tab over persisted A2A runs (2.2) (#12479)

* feat(db): a2a task history module over migration-002 tables

* feat(a2a): persist task lifecycle to a2a_tasks with 30d retention purge

* feat(api): a2a task history listing + historical detail fallback

* feat(dashboard): orchestration History tab (Airflow-grid) over persisted runs (2.2)

* fix(dashboard): assert history preset window + loading and time axis in the grid

* chore(dashboard): history i18n + changelog

* fix(dashboard): explicit history purge cascade + keep live drawer off the History tab

* docs: document OMNIROUTE_A2A_HISTORY_RETENTION_DAYS

* refactor(dashboard): split HistoryTab helpers under the complexity ratchet

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Co-authored-by: Markus Hartung <diegosouzapw@users.noreply.github.com>