feat: 来源归因规则引擎（渠道/AI/搜索词/诚实状态/历史重算）

- constants 规则库 v1：AI/引擎/社交域名表、搜索词参数白名单、付费点击参数、
  应用内 UA 标记、CHANNELS 枚举；page_view 白名单开 nav_type/prerendering
- services/attribution.classify 纯函数：付费>AI>引擎>社交>referral 分层，
  UTM 证据叠加（combined/conflict/label_only），应用内 UA 叠加/兜底，
  引擎 TLD 国家 variant，搜索词白名单提取（Google 恒空不虚构）
- SourceClassification 派生表（迁移 0004）：first_touch/session_entry 双 scope，
  rule_version 可追溯
- ingest 增量 best-effort：首访客/新会话时分类落库（savepoint+静默，
  失败不影响采集）；validation 对 page_view referrer 完整 URL 参数清洗+截500
- recompute_attribution 命令：全量/按站幂等重算
- API：访客列表归因五字段+channel 筛选、详情 attribution 块（含最近5会话入口）、
  dashboard channels 聚合（sources 原口径保留）；TS VisitorListParams 加 channel
- 测试 97 → 124（引擎20 + 集成/接口7）

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

server/tracker/tests/test_ingest.py

@@ -142,3 +142,23 @@ def test_context_timezone_persisted_to_visitor(db):
     b["context"]["timezone"] = "Asia/Shanghai"
     ingest_batch(site, b)
     assert Visitor.objects.get(visitor_id="v1").timezone_name == "Asia/Shanghai"
+
+# 15. 归因分类 best-effort：引擎抛异常不影响采集入库（first_touch/session_entry 双路）
+def test_attribution_failure_never_breaks_ingest(db, monkeypatch):
+    from tracker.services import ingest as ingest_mod
+    site = Site.objects.create(name="s", domains=["a.com"])
+    monkeypatch.setattr(ingest_mod, "classify", lambda **kw: (_ for _ in ()).throw(RuntimeError("boom")))
+    r = ingest_batch(site, _batch([_ev(1)]))
+    assert r["accepted"] == 1 and Event.objects.count() == 1
+    assert Visitor.objects.count() == 1 and VisitSession.objects.count() == 1
+
+# 16. 首触分类用本批第一条 page_view 的完整 referrer（搜索词可恢复），非 ctx 裸域名
+def test_first_touch_classification_uses_full_pageview_referrer(db):
+    from tracker.models import SourceClassification
+    site = Site.objects.create(name="s", domains=["a.com"])
+    b = _batch([_ev(1, properties={"referrer": "https://m.baidu.com/s?wd=挖掘机"})])
+    b["context"]["utm"] = {}     # 默认 fixture 带 utm_source=google，与百度矛盾 → conflict
+    ingest_batch(site, b)
+    ft = SourceClassification.objects.get(scope="first_touch")
+    assert ft.channel == "natural_search" and ft.platform == "百度"
+    assert ft.search_term == "挖掘机" and ft.resolution == "resolved"