v1.2.0

Added

• Archive leg groundwork: a captive stellar-core replay source
  (internal/source/captive) serving bounded history-archive ranges with
  the unified event semantics RPC serves (EMIT_CLASSIC_EVENTS +
  BACKFILL_STELLAR_ASSET_EVENTS), plus boot configuration
  (STELLAR_CORE_BINARY, HISTORY_ARCHIVE_URLS, CAPTIVE_STORAGE_PATH)
  validated at startup.
• Gap healer: with the archive leg enabled, recorded below-retention gaps
  are walked downward in atomic 2000-ledger chunks replayed from the
  archives, with a heal watermark on the gap row and the clamped backfill
  frontiers lowered (and un-clamped) in the same transaction, so declared
  coverage grows exactly as fast as healed data lands. Before the first
  heal the captive replay must prove itself byte-equivalent to the RPC
  on a checkpoint-aligned range both can serve, after normalizing the two
  parts of the meta that are unstable run to run even on identical core
  builds (both proven live): diagnostic events are stripped, and
  ledger-entry-change units are canonically ordered within each
  operation. A divergent replay disables healing
  (sierpe_archive_equivalence_failures_total, alertable) instead of
  filling gaps with unverified data. /status
  reports the leg as archive: off|unverified|verified|equivalence_failed,
  and heals progress through sierpe_gaps_healed_total and
  sierpe_healed_ledgers_total.
• -full image variant (Dockerfile.full, linux/amd64): the appliance
  plus stellar-core, with STELLAR_CORE_BINARY pre-set — deploy it and
  registrations reach below RPC retention out of the box. The slim image
  stays multi-arch and distroless for archive-less deployments.
  Deployment guidance in docs/DEPLOY.md.