feat(adr-004): NIM HTTP 429 → Hermes 規則引擎降級路由

- _call_nim(): 429 不重試，立即拋出讓上層接管
- _hermes_rule_fallback(): 確定性四規則路由（gap/sales/risk 閾值），
  Telegram 告警加 🟡 降級前綴，行為與 NIM system prompt 一致
- dispatch(): 捕捉 HTTPError 429 → 轉 _hermes_rule_fallback()，
  回傳 nim_stats.degraded=True 供監控追蹤

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/nemoton_dispatcher_service.py

@@ -384,6 +384,11 @@ class NemotronDispatcher:
                 break
             except (requests.Timeout, requests.HTTPError) as e:
                 last_err = e
+                # ADR-004: 429 不重試，立即拋出讓上層啟動 Hermes 規則引擎降級
+                if isinstance(e, requests.HTTPError) and e.response is not None \
+                        and e.response.status_code == 429:
+                    logger.warning("[NIM] HTTP 429 速率限制，跳出 retry 迴圈")
+                    raise
                 if _attempt < 2:
                     _time.sleep(2 ** _attempt)
                     logger.warning(f"[NIM] retry {_attempt + 1}/2 after {e}")
@@ -431,6 +436,87 @@ class NemotronDispatcher:
         logger.info(f"[NIM] 收到 {len(results)} 個 tool_calls | tokens={nim_stats['total_tokens']}")
         return results, nim_stats
 
+    # ──────────────────────────────────────────────
+    # ADR-004：Hermes 規則引擎降級路由
+    # ──────────────────────────────────────────────
+    def _hermes_rule_fallback(self, threats: list, hermes_stats: Optional[dict] = None) -> dict:
+        """
+        ADR-004 降級模式：NIM HTTP 429 時，改用確定性規則路由 Hermes 威脅清單。
+        路由規則與 NIM system prompt 一致，所有 Telegram 告警加 🟡 降級前綴。
+
+        Rules（依序判斷，命中即停）：
+          1. gap_pct < 5% 且 sales_delta < -30%  → flag_for_human_review（疑似缺貨/流量異常）
+          2. gap_pct ≥ 5% 且 risk=HIGH           → trigger_price_alert
+          3. gap_pct < 0 且 sales_delta > 0       → add_to_recommendation（我方具競爭力）
+          4. 其餘                                 → flag_for_human_review（信心不足/複雜情況）
+        """
+        degraded_note = "🟡 [降級模式 ADR-004] NIM 配額耗盡，改用 Hermes 規則引擎決策"
+        footprint = degraded_note + "\n" + _build_footprint_block(hermes_stats, None)
+
+        dispatched, errors = 0, []
+
+        for t in threats:
+            try:
+                if t.gap_pct < 5 and t.sales_7d_delta_pct < -30:
+                    # Rule 1：價差微小但銷量大跌 → 非定價問題，人工確認
+                    self._exec_flag_for_human_review(
+                        sku=t.sku, name=t.name,
+                        concern=(
+                            f"🟡 [規則引擎] 價差僅 {t.gap_pct:+.1f}% 但銷量大跌 "
+                            f"{t.sales_7d_delta_pct:+.1f}%，疑似缺貨/下架/平台流量異常，"
+                            "請人工走查前台。"
+                        ),
+                        confidence=0.80,
+                        footprint=footprint,
+                        momo_price=t.momo_price, comp_price=t.pchome_price,
+                        gap_pct=t.gap_pct, sales_delta=t.sales_7d_delta_pct,
+                    )
+                elif t.gap_pct >= 5 and t.risk == "HIGH":
+                    # Rule 2：高價差 HIGH 風險 → 競價告警
+                    self._exec_trigger_price_alert(
+                        t.sku, t.name,
+                        t.gap_pct, t.sales_7d_delta_pct,
+                        f"🟡 [規則引擎] {t.recommended_action}",
+                        t.confidence,
+                        momo_price=t.momo_price, comp_price=t.pchome_price,
+                        footprint=footprint,
+                    )
+                elif t.gap_pct < 0 and t.sales_7d_delta_pct > 0:
+                    # Rule 3：我方具競爭力 + 銷量正成長 → 推薦
+                    self._exec_add_to_recommendation(
+                        t.sku, t.name,
+                        (
+                            f"🟡 [規則引擎] 我方比競品便宜 {abs(t.gap_pct):.1f}%，"
+                            f"銷量正成長 {t.sales_7d_delta_pct:+.1f}%"
+                        ),
+                        t.confidence,
+                        footprint=footprint,
+                        threat=t,
+                    )
+                else:
+                    # Rule 4：其餘複雜情況 → 人工覆核
+                    self._exec_flag_for_human_review(
+                        sku=t.sku, name=t.name,
+                        concern=(
+                            f"🟡 [規則引擎] 情況複雜或信心不足（信心 {t.confidence:.0%}），"
+                            f"建議：{t.recommended_action}"
+                        ),
+                        confidence=t.confidence,
+                        footprint=footprint,
+                        momo_price=t.momo_price, comp_price=t.pchome_price,
+                        gap_pct=t.gap_pct, sales_delta=t.sales_7d_delta_pct,
+                    )
+                dispatched += 1
+            except Exception as e:
+                errors.append(f"fallback({t.sku}): {e}")
+                logger.error(f"[Dispatcher][ADR-004] Hermes fallback 失敗 {t.sku}: {e}")
+
+        logger.info(
+            f"[Dispatcher][ADR-004] Hermes 規則引擎降級完成 "
+            f"dispatched={dispatched} errors={len(errors)}"
+        )
+        return {"dispatched": dispatched, "skipped": 0, "errors": errors, "nim_stats": {"degraded": True}}
+
     # ──────────────────────────────────────────────
     # 語意化訊息格式器
     # ──────────────────────────────────────────────
@@ -825,6 +911,23 @@ class NemotronDispatcher:
 
         try:
             tool_calls, nim_stats = self._call_nim(nim_candidates)
+        except requests.HTTPError as e:
+            if e.response is not None and e.response.status_code == 429:
+                logger.warning("[Dispatcher][ADR-004] NIM HTTP 429，啟動 Hermes 規則引擎降級")
+                fb = self._hermes_rule_fallback(nim_candidates, hermes_stats)
+                return {
+                    "dispatched": dispatched + fb["dispatched"],
+                    "skipped":    skipped + fb["skipped"],
+                    "errors":     errors + fb["errors"],
+                    "nim_stats":  fb["nim_stats"],
+                }
+            logger.error(f"[Dispatcher] NIM HTTP 錯誤: {e}")
+            return {
+                "dispatched": dispatched,
+                "skipped":    len(nim_candidates),
+                "errors":     errors + [str(e)],
+                "nim_stats":  {},
+            }
         except Exception as e:
             logger.error(f"[Dispatcher] NIM 呼叫失敗: {e}")
             return {