feat(fusion_accounting_bank_rec): 4-pass confidence scoring pipeline

Task 11 of Phase 1 Bank Reconciliation. Adds the brain that ranks
candidate journal-item matches for a bank statement line.

Pass 1 — SQL filter (done by caller's _fetch_candidates).
Pass 2 — Statistical scoring: weighted blend of amount-delta,
         partner pattern fit, and precedent similarity.
Pass 3 — Optional AI re-rank when an LLM provider is configured;
         gracefully no-ops when provider missing, prompt module not
         yet present (Task 20), or the JSON response is malformed.
Pass 4 — Persistence (handled by engine.suggest_matches).

Returns top-K ScoredCandidate dataclasses with per-feature scores
exposed for transparency and future learning.

7 new tests added; full module suite green (51 tests, 0 failures).

Made-with: Cursor

fusion_accounting_bank_rec/tests/__init__.py

@@ -4,3 +4,4 @@ from . import test_matching_strategies
 from . import test_ai_suggestion_lifecycle
 from . import test_precedent_lookup
 from . import test_pattern_extraction
+from . import test_confidence_scoring