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/src/db/models.py

@@ -17,7 +17,9 @@ from uuid import uuid4
 from sqlalchemy import (
     JSON,
     BigInteger,
+    CheckConstraint,
     DateTime,
+    Float,
     Index,
     Integer,
     String,
@@ -28,6 +30,7 @@ from sqlalchemy import (
     Enum as SQLEnum,
 )
 from sqlalchemy.dialects.postgresql import ENUM as PgEnum
+from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column
 
 from src.db.base import Base
@@ -179,6 +182,28 @@ class ApprovalRecord(Base):
         comment="匹配的 Playbook ID，學習服務用以更新 EWMA trust score",
     )
 
+    # 2026-04-26 P2-DB-Fix by Claude — db-expert P0 三修（P0.3）: P2.1 DecisionFusionEngine 欄位
+    # composite_score / complexity_tier / decision_fusion_details
+    # 僅在 AIOPS_P2_FUSION_ENABLED=True 且 fusion 成功時填入（nullable=True）
+    composite_score: Mapped[float | None] = mapped_column(
+        Float,
+        nullable=True,
+        comment="P2.1 DecisionFusion 合成分數（0.0-1.0），方法 III 加權結果",
+    )
+    complexity_tier: Mapped[str | None] = mapped_column(
+        String(16),
+        nullable=True,
+        comment="P2.1 告警複雜度分層：low / medium / high / critical",
+    )
+    decision_fusion_details: Mapped[dict | None] = mapped_column(
+        JSONB,
+        nullable=True,
+        comment=(
+            "P2.1 DecisionFusionEngine: openclaw_score / hermes_score / "
+            "playbook_score / mcp_health_score / elephant_score"
+        ),
+    )
+
     # Timestamps
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
@@ -212,6 +237,22 @@ class ApprovalRecord(Base):
             "matched_playbook_id",
             postgresql_where=text("matched_playbook_id IS NOT NULL"),
         ),
+        # 2026-04-26 P2-DB-Fix by Claude — db-expert P0 三修（P0.3）: P2 DecisionFusion 欄位
+        # partial index：fusion fill rate 預期 <50%，只索引有值的行
+        Index(
+            "ix_approval_composite_score",
+            "composite_score",
+            postgresql_where=text("composite_score IS NOT NULL"),
+        ),
+        Index(
+            "ix_approval_complexity_tier",
+            "complexity_tier",
+            postgresql_where=text("complexity_tier IS NOT NULL"),
+        ),
+        CheckConstraint(
+            "complexity_tier IN ('low','medium','high','critical') OR complexity_tier IS NULL",
+            name="chk_complexity_tier",
+        ),
     )