admin: add ledger-range Horizon replay endpoint and docs

[pchieneye]

Admin: add ledger-range Horizon replay endpoint

Body:

• Adds new admin endpoint: POST /api/admin/events/replay-range (validated body: fromLedger, toLedger).
• Implements ReplayService.replayLedgerRange(fromLedger, toLedger, ...) which:
  • Fetches Horizon operations per ledger using Stellar SDK forLedger.
  • Best-effort maps operations to existing replay handlers (bond_creation, withdrawal, attestation) and invokes them.
  • Captures handler failures to the failed-events queue and audit-logs the overall replay run (REPLAY_LEDGER_RANGE).
• Registers handler usage with existing registerAllReplayHandlers behavior; no handler behavioral changes.
• Documents the endpoint in admin-api.md.
• Notes: replay is best-effort; unsupported ops are skipped; errors for individual ops are recorded for later inspection.

Closes: #567

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