temp(versioning): demo version-history dropdowns + French i18n

Adds debug-only ``VersionHistoryDropdown`` widgets to the chart,
dashboard, and dataset list pages so the version surface can be
exercised from the UI during the spike. Each row's actions column
gets a clock-icon dropdown that fetches ``/api/v1/{resource}/<uuid>/
versions/`` on click, lists the ten most recent versions with a
formatted change-log summary, and offers per-version restore via
``POST .../versions/<uuid>/restore``.

Strings are wrapped in ``t('...')`` with placeholder formatting
(e.g. ``t('Added %(kind)s "%(name)s"', { kind, name })``) so
translators can reorder verbs and nouns rather than concatenating
fragments. ``KIND_LABELS`` is a static map keying English layout
kinds (``chart``, ``row``, ``column``, ``tab``, ``markdown``, etc.)
to ``t(...)``-extractable labels. Empty change lists render as
"Baseline" rather than "No changes recorded" since the empty case
is overwhelmingly the ``operation_type=0`` baseline row.

Locale-aware date rendering: ``new Date(iso).toLocaleString(lang)``
where ``lang`` comes from ``document.documentElement.lang`` (set
by ``src/views/App.tsx`` from the bootstrap ``locale``), so dates
follow the user's chosen Superset locale rather than the browser's.

French translations for the new strings are appended to
``superset/translations/fr/LC_MESSAGES/messages.po`` (Ajouté,
Supprimé, Modifié, Version initiale, kind labels, …). Run
``npm run build-translation`` and ``pybabel compile -l fr`` to
regenerate the JSON / MO packs.

This commit is **demo-only** per ADR-005 (V1 is backend-only). It
is intentionally marked ``temp`` so it can be reverted before the
PR splits — the production V1 ships without UI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>