Add query-backed live Data datasets

[czyt]

Scope

• Add private saved datasets backed by a saved read-only Data request; refresh once before collection steps.
• Preserve exact numeric text and backup privacy; fail before any collection request on refresh, cancellation or execution-limit errors.
• Support hosted/native runs, CLI agents, schedules and CI presets with owner, revision and credential checks.
• Add bilingual dataset editing and selection.

Spec: docs/specs/data-live-datasets.md
Coverage: docs/SAVED-DATASETS-COVERAGE.md

Verification

• Local real Data refresh, changed rows, zero-step failure, dynamic step limit, owner isolation, cancellation and privacy fixtures.
• Real CLI agent success, credential revocation and workspace-edit process fixtures; schedule and CI preset tests.
• Frontend suite, production builds, focused server/CLI tests, strict Clippy and format checks.
• 390px English/Chinese browser save, reload and run; no horizontal overflow. Chinese editor automated WCAG A/AA check found zero violations and one obscured element requiring manual assessment.
• Independent review findings fixed and re-reviewed; local integration against current main passed.
• Application CI run 38982703929 completed source, full check and three-database jobs successfully at 578a8c2; Docker amd64/arm64 image jobs and worker passed at the same head.

Remaining wider gates

• Current native platform packages and full release verification remain tracked separately.
• Browser editing the Data source after initial save was not exercised; the real backend next-run refresh passed.