feat(wave6-8): P2.1 fusion + P2.2 governance + P2.4 consensus + Wave 7/8 BLOCKER 修復

承接 Wave 6/7/8 多 engineer 在 agent 限額前完成的代碼，補 commit 解 production
HEAD 隱性 import error（decision_fusion 已被 decision_manager 引用但檔案 untracked）。

新增（後端核心）:
- decision_fusion.py (562 行) — P2.1 方法 III（OpenClaw + Hermes + Elephant 三 LLM 融合）
- aiops_timeline.py + aiops_timeline_service.py — critic B4 修復
  /api/v1/aiops/timeline endpoint，DB 存取抽到 service 層遵守 leWOOOgo 積木化
- migrations/p2_decision_fusion_columns.sql + rollback — approval_records fusion 欄位

修改（後端整合）:
- decision_manager.py — fusion 三斷鏈修補（critic B1+B2+B3）：
  · B1: 寫 _evidence_snapshot_ref 到 token.proposal_data
  · B2: fusion 前計算 complexity_score 並寫 token
  · B3: fusion composite 寫 token.proposal_data["decision_fusion"]
- auto_approve.py — fusion + consensus 認識（critic B3+B5）：
  · composite > 0.7 → auto_execute_eligible bypass min_confidence
  · source=consensus_engine + score>=0.6 → 規則可信路徑
- consensus_engine.py — db-fix _save_consensus 重用 agent_sessions
- governance_agent.py — db-fix _alert PG 寫入 ai_governance_events
- approval_db.py — fusion 3 欄位 + 2 partial index + CheckConstraint
- db/models.py — schema 對齊 migration
- core/config.py — vuln #1 修復：OLLAMA_URL/_FALLBACK_URL field_validator
  拒絕公網 IP + 外部域名，僅允許私網/loopback/K8s SVC 白名單
- core/feature_flags.py — P2 fusion + consensus flags
- main.py — governance_agent lifespan 啟動
- failover_alerter.py — Wave8-X2: in-memory dedup fallback（Redis 拒絕後不 fail-open）
- ollama_*.py — metrics 整合 + recovery 改善
- auto_repair_service.py — verifier 接線

新增（測試 2438 行）:
- test_decision_fusion.py / test_governance_agent.py / test_consensus_integration.py
- test_p2_db_fixes.py / test_wave8_fusion_fixes.py
- test_config_url_validation.py（vuln #1 12 tests）
- test_failover_alerter.py +Wave8-X2 in-memory dedup 補測

驗收: 116 tests pass (decision_fusion + wave8_fusion + config_url + consensus +
                      governance + p2_db_fixes + failover_alerter)

Conflict resolution:
- 3 檔（config.py + auto_approve.py + decision_manager.py）git stash pop 衝突
  保留 stashed (engineer 最終版)，補回 ValueError 「公網 IP」字樣對齊 test

Note: 此 commit 解 production HEAD 隱性 import error
仍未修: vuln #4 prompt injection / debugger B14 quota fail-closed
       / B25-B26 drain_pending_tasks / B8 governance fail alert

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Multiple Engineers (Wave 6/7/8) <noreply@anthropic.com>

apps/api/migrations/p2_decision_fusion_columns.sql

@@ -0,0 +1,38 @@
+-- p2_decision_fusion_columns.sql
+-- 2026-04-26 P2-DB-Fix by Claude — db-expert P0 三修（P0.3）
+-- P2.1 DecisionFusionEngine 必要欄位 + partial index
+-- ADR-085 鐵律：AI 學習成果不可存 Cache，fusion 分數必須落地 PG
+--
+-- 執行方式：DBA 手動執行（禁止 alembic upgrade / CI 自動跑）
+-- CONCURRENTLY 必須在 transaction 外單獨執行
+
+BEGIN;
+
+ALTER TABLE approval_records
+    ADD COLUMN IF NOT EXISTS composite_score        REAL,
+    ADD COLUMN IF NOT EXISTS complexity_tier        VARCHAR(16),
+    ADD COLUMN IF NOT EXISTS decision_fusion_details JSONB;
+
+ALTER TABLE approval_records
+    ADD CONSTRAINT IF NOT EXISTS chk_complexity_tier CHECK (
+        complexity_tier IS NULL
+        OR complexity_tier IN ('low', 'medium', 'high', 'critical')
+    );
+
+COMMENT ON COLUMN approval_records.composite_score
+    IS 'P2.1 DecisionFusion 合成分數（0.0-1.0），方法 III 加權結果';
+COMMENT ON COLUMN approval_records.complexity_tier
+    IS 'P2.1 告警複雜度分層：low / medium / high / critical';
+COMMENT ON COLUMN approval_records.decision_fusion_details
+    IS 'P2.1 DecisionFusionEngine: openclaw_score / hermes_score / playbook_score / mcp_health_score / elephant_score';
+
+COMMIT;
+
+-- CONCURRENTLY 必須在 transaction 外執行（不可放在 BEGIN/COMMIT 內）
+CREATE INDEX CONCURRENTLY IF NOT EXISTS ix_approval_composite_score
+    ON approval_records (composite_score)
+    WHERE composite_score IS NOT NULL;
+
+CREATE INDEX CONCURRENTLY IF NOT EXISTS ix_approval_complexity_tier
+    ON approval_records (complexity_tier)
+    WHERE complexity_tier IS NOT NULL;

apps/api/migrations/p2_decision_fusion_columns_rollback.sql

@@ -0,0 +1,19 @@
+-- p2_decision_fusion_columns_rollback.sql
+-- 2026-04-26 P2-DB-Fix by Claude — db-expert P0 三修（P0.3）rollback
+-- 回滾 p2_decision_fusion_columns.sql
+
+BEGIN;
+
+ALTER TABLE approval_records
+    DROP CONSTRAINT IF EXISTS chk_complexity_tier;
+
+ALTER TABLE approval_records
+    DROP COLUMN IF EXISTS composite_score,
+    DROP COLUMN IF EXISTS complexity_tier,
+    DROP COLUMN IF EXISTS decision_fusion_details;
+
+COMMIT;
+
+-- CONCURRENTLY 必須在 transaction 外
+DROP INDEX CONCURRENTLY IF EXISTS ix_approval_composite_score;
+DROP INDEX CONCURRENTLY IF EXISTS ix_approval_complexity_tier;