refactor(api): trailing newlines + hoist clearhouse.py parser imports

Self-review nits from Checkpoint 2b:
- All three new router files lacked a trailing newline (same nit as 2a).
- clearhouse.py had lazy imports of serialize_837 / parse /
  db as _db inside helper bodies. Hoisted serialize_837 and
  parse to module-level (no import cycle risk: clearhouse.py does
  not import from cyclone.api). Dropped the redundant db as _db
  alias — the top-level from cyclone import db is already in scope.

No behavior change. test_clearhouse_api: 10 / 10 passing.

backend/src/cyclone/api_routers/clearhouse.py

@@ -23,6 +23,8 @@ from fastapi import APIRouter, HTTPException
 
 from cyclone import db
 from cyclone.audit_log import AuditEvent, append_event
+from cyclone.parsers.parse_837 import parse
+from cyclone.parsers.serialize_837 import serialize_837
 from cyclone.store import store
 
 router = APIRouter()
@@ -99,16 +101,12 @@ def submit_to_clearhouse(body: dict):
 
 
 def _serialize_claim_for_submit(claim_id: str) -> str:
-    """Serialize a claim to X12 for SFTP submission. Lazy import of the
-    serializer to avoid pulling FastAPI machinery at module import time."""
-    from cyclone import db as _db
-    with _db.SessionLocal()() as s:
-        row = s.get(_db.Claim, claim_id)
+    """Serialize a claim to X12 for SFTP submission."""
+    with db.SessionLocal()() as s:
+        row = s.get(db.Claim, claim_id)
         if row is None:
             raise ValueError(f"claim {claim_id!r} not found")
-        # Re-parse the stored raw_json to get a ClaimOutput
         raw = row.raw_json or {}
-        # Reconstruct minimal ClaimOutput from raw_json; this is best-effort.
         return _serialize_claim_from_raw(row, raw)
 
 
@@ -116,19 +114,13 @@ def _serialize_claim_from_raw(claim_row, raw: dict) -> str:
     """Best-effort serializer that uses the stored raw_json to emit a fresh 837.
 
     For SP9 this delegates to the existing serialize_837 helper if the
-    claim has a complete raw_segments array. Otherwise it returns a
-    minimal placeholder.
+    claim has a complete raw_segments array. Otherwise it raises.
     """
-    from cyclone.parsers.serialize_837 import serialize_837
-    from cyclone.parsers.parse_837 import parse
-
-    # Re-parse the original batch text (need to re-derive from store).
     # SP9 stub: if the claim has a `raw_json` with `x12_text`, use that.
     if isinstance(raw, dict) and raw.get("x12_text"):
         result = parse(raw["x12_text"])
         if result.claims:
             return serialize_837(result.claims[0])
-    # Fallback: raise so the caller sees an error.
     raise RuntimeError(
         f"claim {claim_row.id!r} cannot be re-serialized: no stored x12_text"
-    )
+    )

backend/src/cyclone/api_routers/config.py

@@ -53,4 +53,4 @@ def list_payer_configs(payer_id: str):
         live = store.get_payer_config(payer_id, tx)
         if live is not None:
             configs.append({"transaction_type": tx, "config_json": live, "source": "db"})
-    return configs
+    return configs

backend/src/cyclone/api_routers/providers.py

@@ -46,4 +46,4 @@ def list_providers(
         "total": total,
         "returned": returned,
         "has_more": has_more,
-    }
+    }