feat(canopy): send health_details (sizes, fixes, duration) with verification

[passcod]

🤖 Stacks on #87. Canopy accepts an arbitrary health_details map on
/restore-verification, and bestool-canopy 0.4.4 adds a generic request
escape hatch (bestool#626). The typed RestoreVerification struct has no
health_details field, so pgro serializes the typed report, splices in
health_details, and POSTs the merged body via CanopyClient::request
to the same endpoint.

health_details (snake_case)

• sizes — per-database on-disk bytes (pg_database_size), keyed by
  db name.
• fixes — an arbitrary jsonb map of the fix steps the restore
  applied: locale, reindex, reset_wal, recreated_pg_wal. Stored
  in _pgro.restore_info.fixes by the init script and forwarded
  verbatim, so adding a fix later is one shell line + its flag file —
  no schema change, no operator change. (reindex/locale were the
  example; this carries whatever we apply.)
• restore_duration_sec — wall-clock from the restore CR's
  createdAt to report time (≈ activation).

Gathering

sizes + fixes come from a single read-only connection to the
restore's postgres, done in the switchover block before #87's
ephemeral teardown destroys the DB. Best-effort: on the failure path (or
if postgres never came up) those pieces are omitted and the verification
still sends. restore_duration_sec is independent of postgres.

Records pg_resetwal / pg_wal-recreation via flag files so they
surface in fixes next to the existing locale/reindex flags.

Follow-up: typed schema (bestool#628)

This uses the arbitrary-JSON request path. Once bestool#628 lands and
releases (build-time bestool_canopy::schema:: types generated from
canopy's OpenAPI), a follow-up will swap the hand-built Value for the
generated RestoreVerification type + request_json, for compile-time
safety against canopy's spec. Deliberately not blocking this PR on it.

More stats?

Easy follow-ups if you want them (all cheap from the same connection):
per-db table count, largest-relation size, pg_stat_database xact/blks
counters, or the snapshot→restored size ratio.