feat(sp10): 277CA parser + Payer-Rejected Inbox lane

- Add cyclone.parsers.models_277ca + parse_277ca (X12 005010X214)
  - Per-Patient HL ClaimStatus with REF*1K (PCN), REF*EJ (tax ID),
    STC category code, amount, service date
  - STC classifier: A1-A3 accepted, A4/A6/A7 rejected, A8/A9 pended,
    P1-P5 paid, anything else unknown
  - Multiple STCs per Patient HL: last wins (canonical pattern for
    'first pended, then paid' acknowledgments)
  - Subscriber-level STCs surface in unscoped_statuses
- Add apply_277ca_rejections — stamps Claim.payer_rejected_* fields on
  matching rows (lookup by patient_control_number, mirrors 999 path)
- New /api/parse-277ca, /api/277ca-acks, /api/277ca-acks/{id} endpoints
- New two77ca_acks table + Two77caAck ORM model
- New Claim columns: payer_rejected_at, _reason, _status_code, _by_277ca_id
- New payer_rejected lane in /api/inbox/lanes (distinct from 999
  envelope rejected lane)
- New PayerConfig277CA block in config/payers.yaml + Pydantic model
- Migration 0008 bumps user_version to 8

Tests: 654 -> 688 (parser 22 + apply 6 + API 8 + config 6 + adjustments).
All 688 backend tests pass; 1 pre-existing skipped test class unaffected.

backend/tests/fixtures/minimal_277ca.txt

@@ -0,0 +1,42 @@
+ISA*00*          *00*          *ZZ*COMEDICAID     *ZZ*DZINESCO       *240620*1200*^*00501*000000123*0*P*:~
+GS*HN*COMEDICAID*DZINESCO*20240620*1200*1*X*005010X214~
+ST*277CA*0001*005010X214~
+BHT*0085*08*REFNUM001*20240620*1200*TH~
+HL*1**20*1~
+NM1*PR*2*COLORADO MEDICAL ASSIST*****PI*COMEDICAID~
+TRN*2*REFNUM001~
+DTP*050*RD8*20240601-20240630~
+DTP*009*RD8*20240601-20240630~
+HL*2*1*21*1~
+NM1*41*2*DZINESCO*****46*11525703~
+TRN*2*REFNUM001~
+HL*3*2*19*1~
+NM1*IL*1*DOE*JOHN****MI*MEMBERID001~
+TRN*2*TRACE001~
+HL*4*3*PT~
+NM1*QC*1*DOE*JANE~
+REF*1K*CLAIM001~
+REF*EJ*721587149~
+STC*A3:19:PR*20240620*WQ*100.00~
+QTY*90*1~
+AMT*YU*100.00~
+DTP*472*RD8*20240615-20240615~
+HL*5*3*PT~
+NM1*QC*1*SMITH*ROBERT~
+REF*1K*CLAIM002~
+REF*EJ*721587149~
+STC*A6:19:PR*20240620*U*250.00~
+QTY*90*1~
+AMT*YU*250.00~
+DTP*472*D8*20240610~
+HL*6*3*PT~
+NM1*QC*1*GARCIA*MARIA~
+REF*1K*CLAIM003~
+REF*EJ*721587149~
+STC*A8:19:PR*20240620*U*175.50~
+QTY*90*1~
+AMT*YU*175.50~
+DTP*472*RD8*20240612-20240612~
+SE*40*0001~
+GE*1*1~
+IEA*1*000000123~

backend/tests/fixtures/minimal_277ca_rejected_only.txt

@@ -0,0 +1,14 @@
+ISA*00*          *00*          *ZZ*COMEDICAID     *ZZ*DZINESCO       *240620*1200*^*00501*000000789*0*P*:~
+GS*HN*COMEDICAID*DZINESCO*20240620*1200*3*X*005010X214~
+ST*277CA*0001*005010X214~
+BHT*0085*08*REFNUM003*20240620*1200*TH~
+HL*1**20*1~
+HL*2*1*21*1~
+HL*3*2*19*1~
+HL*4*3*PT~
+REF*1K*CLAIM099~
+REF*EJ*721587149~
+STC*A7:19:PR*20240620*U*99.99~
+SE*8*0001~
+GE*1*1~
+IEA*1*000000789~

backend/tests/fixtures/minimal_277ca_st277.txt

@@ -0,0 +1,15 @@
+ISA*00*          *00*          *ZZ*COMEDICAID     *ZZ*DZINESCO       *240620*1200*^*00501*000000456*0*P*:~
+GS*HN*COMEDICAID*DZINESCO*20240620*1200*2*X*005010X214~
+ST*277*0001*005010X214~
+BHT*0085*08*REFNUM002*20240620*1200*TH~
+HL*1**20*1~
+NM1*PR*2*COLORADO MEDICAL ASSIST*****PI*COMEDICAID~
+HL*2*1*21*1~
+HL*3*2*19*1~
+HL*4*3*PT~
+REF*1K*CLAIM004~
+REF*EJ*721587149~
+STC*A3:19:PR*20240620*WQ*300.00~
+SE*10*0001~
+GE*1*1~
+IEA*1*000000456~