feat: 移动端设备信息最大化采集（型号/UA-CH/视口/方向/触点/内存/网络/深浅色）

SDK：buildEnvContext 同步扩展 12 键（dpr/viewport/orientation/maxTouchPoints/
deviceMemory/languages/colorScheme/standalone/network downlink·rtt·saveData/
微信版本），逐键 try/catch 静默缺则不挂；新增 collectHighEntropyHints（UA-CH
model/platformVersion/architecture/bitness），init 后 Promise.race 2s 超时
异步并入 __ctk_ctx——批次 context flush 时读取，不阻塞首屏。

后端：Visitor 加 device_model/env_extra（迁移 0005）；ingest 首批快照
EXTENDED_ENV_KEYS 白名单（值截 100），非首批不覆盖、唯 device_model 空且
本批有值时补填一次（晚到 hints）；列表/详情 API 随行输出。

前端：详情访问环境卡设备行升级显示型号（手机 · Pixel 7），追加像素比/
视口/屏幕方向/触点/内存/网络质量/深浅色/微信版本行（env_extra 逐键判空，
旧数据整块不显示）；列表设备列主行拼型号（手机·Pixel 7）。

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

server/tracker/tests/test_visitors.py

@@ -78,7 +78,8 @@ def test_list_fields_and_default_bot_excluded(client, member_user):
                         "device_type", "os", "browser", "language", "first_seen_at",
                         "last_seen_at", "visit_count", "active_days", "session_count",
                         "total_stay_ms", "first_source", "last_source", "first_landing_path",
-                        "online", "channel", "platform", "variant", "search_term", "resolution"}
+                        "online", "channel", "platform", "variant", "search_term", "resolution",
+                        "device_model"}
     assert row["country"] == "中国" and row["os"] == "Windows" and row["browser"] == "Chrome"
     assert row["session_count"] == 2
     assert row["total_stay_ms"] == 150000            # 120000+30000，有效停留口径
@@ -429,3 +430,26 @@ def test_detail_source_evidence_no_classification(client, member_user):
     assert attr["first_observable"] == {"channel": "unknown", "resolution": "unknown"}
     assert attr["first_identifiable"] is None
     assert attr["latest_session"] is None
+
+
+def test_device_model_and_env_extra_fields(client, member_user):
+    """设备型号/扩展环境快照：新数据随行输出；旧访客空串/空对象（前端逐键判空跳行）。"""
+    _auth(client, member_user)
+    site = Site.objects.create(name="s", domains=["a.com"])
+    _visitor(site, "v-new", last_seen=timezone.now(), device_model="Pixel 7",
+             env_extra={"viewport": "393x851", "device_pixel_ratio": "2.625",
+                        "color_scheme": "dark", "network_downlink": "10",
+                        "network_rtt": "50", "save_data": "0", "wechat_version": "8.0.49"})
+    _visitor(site, "v-old", last_seen=timezone.now() - timedelta(hours=1))
+
+    d = client.get("/api/admin/visitors").json()["data"]
+    by_id = {x["visitor_id"]: x for x in d["list"]}
+    assert by_id["v-new"]["device_model"] == "Pixel 7"   # 列表行随带（设备列小字用）
+    assert by_id["v-old"]["device_model"] == ""
+
+    d = client.get("/api/admin/visitors/v-new").json()["data"]
+    assert d["device_model"] == "Pixel 7"
+    assert d["env_extra"]["viewport"] == "393x851"
+    assert d["env_extra"]["network_rtt"] == "50"
+    d = client.get("/api/admin/visitors/v-old").json()["data"]
+    assert d["device_model"] == "" and d["env_extra"] == {}