feat(admin): 访客详情页按客迹视觉V1重设计（头部卡/统计卡/时间线/来源证据三口径/访问环境）

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

server/tracker/api/visitors.py

@@ -208,6 +208,31 @@ class VisitorListView(EnvelopeMixin, APIView):
         return ok({"list": rows, "total": total, "page": page})
 
 
+def _source_evidence_triplet(visitor, ft, entries):
+    """来源证据三口径（详情页「来源证据」卡的数据面）。
+
+    first_observable   首次可观测来源：first_touch 分类原样（含 direct/unknown——诚实展示
+                       "首访只观察到直接访问"）；无分类行（历史数据未重算）→ unknown 占位。
+    first_identifiable 首次可识别来源：first_touch 本身可识别（resolved/label_only/conflict，
+                       即除"没认出来"外的全部状态）直接用；否则回溯最早一条可识别的会话入口
+                       ——首访 direct 不算"可识别"，后续某天才带上可识别来源是常见轨迹。
+                       都没有 → None（前端显示 —，不虚构）。
+    latest_session     本次会话来源：最新一条会话入口分类；无 → None。
+    """
+    first_observable = _classification(ft) or {"channel": "unknown", "resolution": "unknown"}
+    if ft and ft.resolution in ("resolved", "label_only", "conflict"):
+        first_identifiable = _classification(ft)
+    else:
+        earliest = (SourceClassification.objects
+                    .filter(visitor=visitor, scope="session_entry",
+                            resolution__in=("resolved", "label_only"))
+                    .select_related("session")
+                    .order_by("session__started_at", "pk").first())
+        first_identifiable = _classification(earliest, with_session=True)
+    latest_session = _classification(entries[0], with_session=True) if entries else None
+    return first_observable, first_identifiable, latest_session
+
+
 class VisitorDetailView(EnvelopeMixin, APIView):
     def get(self, request, visitor_id):
         visitor = _annotate(Visitor.objects.filter(visitor_id=visitor_id)
@@ -222,16 +247,24 @@ class VisitorDetailView(EnvelopeMixin, APIView):
         cutoff = timezone.now() - ONLINE_WINDOW
         ft = (SourceClassification.objects.filter(visitor=visitor, scope="first_touch")
               .first())
-        entries = (SourceClassification.objects
-                   .filter(visitor=visitor, scope="session_entry")
-                   .select_related("session")            # session_id 随行带出，免逐行查询
-                   .order_by("-session__started_at", "-pk")[:ATTR_SESSION_ENTRIES])
+        entries = list(SourceClassification.objects
+                       .filter(visitor=visitor, scope="session_entry")
+                       .select_related("session")            # session_id 随行带出，免逐行查询
+                       .order_by("-session__started_at", "-pk")[:ATTR_SESSION_ENTRIES])
+        first_observable, first_identifiable, latest_session = \
+            _source_evidence_triplet(visitor, ft, entries)
         return ok({**_row(visitor, last_session, cutoff, ft),
+                   # 浏览页面数：page_view 事件计数（page_stay 不并计——它是停留信号不是浏览）
+                   "pages_viewed": Event.objects.filter(
+                       visitor=visitor, event_name="page_view").count(),
                    "screen": visitor.screen, "timezone_name": visitor.timezone_name,
                    "last_ip": visitor.last_ip, "first_utm": visitor.first_utm or {},
                    "first_landing_path": visitor.first_landing_path,
                    "first_referrer_domain": visitor.first_referrer_domain,
                    "attribution": {"first_touch": _classification(ft),
+                                   "first_observable": first_observable,
+                                   "first_identifiable": first_identifiable,
+                                   "latest_session": latest_session,
                                    "session_entries": [_classification(e, with_session=True)
                                                        for e in entries]},
                    "sessions": [_session_summary(s) for s in sessions]})