feat(ws6): Hermes observability — latency logging + dispatch audit table

- nl_gateway.py: time.monotonic() 測量 SDK call 耗時
  hermes_nl_dispatch log 加 latency_ms + success 欄位
- migrations/adr094_hermes_dispatch_log.sql
  hermes_dispatch_log（bigserial + chat_id/user_id/agent/latency_ms/success）
  已部署至 prod awoooi_prod
  ADR-094 P95 latency 監控 + 幻覺追蹤用

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

apps/api/src/hermes/nl_gateway.py

@@ -6,6 +6,7 @@ Layer 1 意圖路由（關鍵字正則）→ Claude Agent SDK 呼叫 → Telegra
 """
 from __future__ import annotations
 import re
+import time
 
 import structlog
 from claude_agent_sdk import query, ClaudeAgentOptions
@@ -93,15 +94,10 @@ async def process_nl_message(
         agent_name = DEFAULT_AGENT
         system_prompt = get_agent_system_prompt(agent_name) or ""
 
-    logger.info(
-        "hermes_nl_dispatch",
-        agent=agent_name,
-        user_id=user_id,
-        chat_id=chat_id,
-        username=username,
-    )
+    t0 = time.monotonic()
 
     # 呼叫 Claude Agent SDK
+    success = False
     try:
         options = ClaudeAgentOptions(
             system_prompt=system_prompt,
@@ -117,6 +113,7 @@ async def process_nl_message(
 
         if not result_text:
             result_text = "_Agent 回應為空，請稍後再試。_"
+        success = True
 
     except Exception as exc:
         logger.error(
@@ -127,6 +124,17 @@ async def process_nl_message(
         )
         result_text = f"_Hermes 暫時無法連線（{type(exc).__name__}），請稍後再試。_"
 
+    latency_ms = int((time.monotonic() - t0) * 1000)
+    logger.info(
+        "hermes_nl_dispatch",
+        agent=agent_name,
+        user_id=user_id,
+        chat_id=chat_id,
+        username=username,
+        latency_ms=latency_ms,
+        success=success,
+    )
+
     header = format_response_header(agent_name)
     # Telegram 訊息上限 4096 字元，超過截斷
     body = result_text[:3800]