feat(manifold): add matcher versioning to separate legacy accepted matches from v3_outcome_guard metrics

Add MANIFOLD_MATCHER_VERSION="v3_outcome_guard" tag persisted to
manifold_match_audit.matcher_version so metrics can isolate current-matcher
stats from pre-versioning records, whose accepted matches the outcome
guard would now reject.

- schema: add matcher_version column + index; idempotent startup backfill
  tagging NULL rows as legacy_pre_outcome_guard (no outcome types) or
  v2_outcome_guard_no_version (has outcome type, version not persisted)
- save_manifold_audit: write matcher_version on every new record
- get_manifold_matches: split summary into current_version / all_time /
  legacy; recent_matches now carry matcher_version

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

bot/strategy/bayesian.py

@@ -19,7 +19,7 @@ from typing import Optional, TYPE_CHECKING
 
 from bot.data.polymarket import Market, market_family_key
 from bot.data.external import ExternalSignals
-from bot.data.manifold import ManifoldMatchResult
+from bot.data.manifold import MANIFOLD_MATCHER_VERSION, ManifoldMatchResult
 
 if TYPE_CHECKING:
     from bot.data.news import NewsClient
@@ -472,6 +472,7 @@ class BayesianStrategy:
                             match_status=manifold_result.status,
                             poly_outcome_type=manifold_result.poly_outcome_type,
                             mfld_outcome_type=manifold_result.mfld_outcome_type,
+                            matcher_version=MANIFOLD_MATCHER_VERSION,
                         )
                     except Exception as exc:
                         log.warning("Failed to save manifold audit: %s", exc)