Adds:
- claims.rejection_reason, claims.rejected_at, claims.resubmit_count
- claims.state_changed_at (was missing, needed for Done-today lane)
- ix_claims_state_changed_at composite index
Also fixes the ClaimState count assertion in test_db_models.py
(7 → 8) to match the REJECTED enum value added in the previous
commit, and bumps the user_version expectation in test_acks.py
(3 → 4) for the same reason.
Three related changes for real CO Medicaid data:
1. Drop UNIQUE(batch_id, patient_control_number) on claims and
UNIQUE(batch_id, payer_claim_control_number) on remittances. The X12
spec allows multiple CLM segments per 2000B subscriber loop and 835
ERAs can repeat a payer_claim_control_number for reversals. Claim/
remittance identity is provided by the primary key (claims.id = CLM01,
remittances.id = CLP01).
2. Add validator rule R835_MULTI_BPR warning for files with multiple BPR
segments (CO Medicaid split-payment pattern). The parser already sums
BPR02 paid_amounts; this surfaces the non-standard data to operators.
3. Skip R835_BAL_BPR_vs_CLP04 when BPR01='I' (Information Only 835).
In that mode BPR02 is informational and the per-claim CLP04 totals
are authoritative — a diff is expected, not an error.
Migration 0003 handles the drop with IF EXISTS so fresh DBs skip cleanly.
Updates affected tests to reflect new schema (no UNIQUE constraint on
batch_id + patient_control_number / payer_claim_control_number).
Fixes test_api_835::test_prodfile_round_trip_persists_separately which
was failing on real production data.
Tyler