feat(sp33): cli resubmit-rejected-claims + fixture/test payer_id refresh

- Adds `cyclone resubmit-rejected-claims` to push corrected single-claim
  837 files to the Gainwell ToHPE SFTP dir. Idempotent (stat-then-skip by
  byte size). One persistent paramiko session per batch with
  reconnect-every=50 to dodge MOVEit's silent per-session file cap
  (~200 puts/session, no exception).
- Validates each file via `parse_837` before upload and rejects any
  whose payer_id is not `CO_TXIX` (catches a bad byte-fix early).
- Refreshes test fixtures (`minimal_837p.txt`, `co_medicaid_837p.txt`,
  `co_medicaid_837p_with_renderer.txt`) and the corresponding test
  assertions (`test_payer.py`, `test_payer_summary.py`,
  `test_co_medicaid_fixture.py`, `test_parse_837.py`) from the old
  `SKCO0`/`COHCPF` payer IDs to `CO_TXIX`, matching
  PayerConfig.co_medicaid() and the HCPF 837P Companion Guide.
- Adds `ingest/` to .gitignore — local scratch / production-data
  staging only.

backend/tests/test_co_medicaid_fixture.py

@@ -36,5 +36,5 @@ def test_subscriber_payer_reused_across_claims():
     result = parse(FIXTURE.read_text(), PayerConfig.co_medicaid())
     assert result.claims[0].billing_provider.npi == "1881068062"
     assert result.claims[1].billing_provider.npi == "1881068062"
-    assert result.claims[0].payer.id == "SKCO0"
-    assert result.claims[1].payer.id == "SKCO0"
+    assert result.claims[0].payer.id == "CO_TXIX"
+    assert result.claims[1].payer.id == "CO_TXIX"