feat(workflow): persist default_view and add a set-default-view endpoint #8014

Task Summary

Let the backend remember, per workflow, which view opens by default (canvas or form) and expose setting it. The Form View is available for every workflow — with no exposed inputs it is simply a one-click run page (Run + results) — so this column is a default-entry preference, not a capability gate: it never gates availability and nothing redirects away from the form.

• migration sql/updates/44.sql: ALTER TABLE workflow ADD COLUMN default_view VARCHAR NOT NULL DEFAULT 'CANVAS' (values: CANVAS, FORM)
• WorkflowResource: PUT /set-default-view/{wid} sets it (write access required; accepts CANVAS/FORM); the update touches only this column. A plain save preserves the stored value and never changes it; a duplicate and a hub-clone both inherit it.
• WorkflowVersionResource: cloneVersion carries the current default_view onto the new workflow (its content comes from the chosen version); the value is a per-workflow preference, not stored per revision.
• UnifiedResourceSchema, WorkflowSearchQueryBuilder: include it in listing/search, so the dashboard can route/badge without parsing each workflow's content.
• The Form View's actual definition lives in content.formBinding; only this default-view preference is denormalized into a column.

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other