v1.3.0

Added

• GET /v1/contracts: list every registration with its classification
  and kinds, so consumers (and the new UI) can enumerate what the
  instance watches without knowing ids upfront.
• Embedded management UI at /: one self-contained HTML page baked into
  the binary (no build system, no external assets) covering the whole
  surface — live instance status, the contract list with classification,
  coverage and counts, a data explorer with a tab per kind (events,
  transfers, state and its history, trustlines and theirs) with filters
  and cursor pagination, and contract registration/unregistration behind
  an admin-token field the page holds only in memory. Reads work without
  credentials, matching the open-reads access model.