feat: SAC detection on transfers and Python SDK client

[BigNathan1]

Summary

Adds SAC (Stellar Asset Contract) detection on transfers and a Python REST client.

closes #136
closes #139

#136 — SAC detection

• New src/indexer/sac-detect.ts classifies a contract as a SAC by reading its
  contract-instance ledger entry and checking whether the executable is the
  built-in ContractExecutableStellarAsset (a SAC wrapping a classic asset)
  rather than uploaded Wasm (a native Soroban token).
• Native XLM SACs are treated as known SACs to avoid an RPC round-trip; results
  are cached per contract since SAC status is immutable; the instance fetcher is
  injectable for testing.
• isSac is exposed as a column on TokenTransfer (new Prisma field +
  migration) and is selectable via the transfers API. The indexer tags each
  transfer during ingest as a best-effort step that never blocks indexing.
• Note: the IndexerCheckpoint model on main was missing its closing brace, so
  the Prisma schema did not validate and no client could be generated. Closing
  that model was required to ship the new column.

#139 — Python SDK client

• New clients/python/ package wraith-py wrapping the REST API in typed
  dataclasses (Transfer, TransferPage, AccountSummary, AssetHolding,
  PopularAssets, PopularAsset). Amounts are kept as strings to preserve full
  i128 precision.
• WraithClient covers transfers (incoming/outgoing/address/tx),
  accounts (summary/transfers), and assets (popular). Non-2xx responses
  raise WraithAPIError. Ships a py.typed marker for PEP 561.
• Packaging via pyproject.toml plus a publish-python-sdk.yml workflow that
  tests then publishes to PyPI via OIDC trusted publishing on pyclient-v* tags.

Testing

• npx tsc --noEmit — clean
• npx jest — all unit suites pass; new sacDetect suite added
• pytest (clients/python) — 7 passing

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[Miracle656]

Reviewed — excellent PR, and thank you for catching the broken schema. Confirmed: IndexerCheckpoint on main was missing its closing brace + @@schema (a bad auto-merge when #133 landed), leaving the Prisma schema invalid. This PR restores it (verified: braces balance, all 11 models closed).

SAC detection (#136): sound approach — executableIsSac checks ContractExecutableStellarAsset vs Wasm, native-XLM SAC IDs are hardcoded to skip an RPC round-trip, status is cached per contract (immutable), and the instance fetcher is injectable for tests. The indexer tagging is correctly best-effort/non-blocking (.catch → defaults false, never blocks ingest). isSac column + migration look right.

Python client (#139): typed dataclasses, string amounts to preserve i128 precision, WraithAPIError on non-2xx, py.typed, and OIDC trusted-publishing workflow. Complete.

Closes #136 and #139. Merging.