fix(v2): 修复预审模型字段表三处缺陷并留出工具预算余量

- 补 8 个标准字段（还款来源/涉诉/增信/保证金/保险/客户名称），对齐原生方法文档声明的 inputs
- 字段守卫改为比对标准字段表，不再把"标准字段但本次无数据"误判为未知字段
- 向模型下发 standard_fields 并在提示词约束字段名，避免自造派生指标
- 补 insurance./deposit. 维度前缀；方案预算 12→18、120s→180s，版本升 1.1.0

实测（临时库 + DeepSeek）：模型类技能由 failed 转为 partial（部分 unknown 属如实标注），
降级记录为空，工具调用 11 次。字段表三处为代码层改动，对既有库即时生效。
验证：scripts/verify.py 11/11 PASS，531 项单测。

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

backend/services/project_assistant.py

@@ -21,8 +21,8 @@ TERMINAL = {"completed", "partial", "failed", "cancelled"}
 REVIEW_TOPICS = (
     {"id": "subject", "title": "主体信息", "prefixes": ("project.", "customer.", "corporate.")},
     {"id": "financial", "title": "财务与现金流", "prefixes": ("financial.", "due_diligence.", "metrics.")},
-    {"id": "lease_asset", "title": "租赁物", "prefixes": ("lease.", "asset.")},
-    {"id": "enhancement", "title": "增信措施", "prefixes": ("guarantee.", "enhancement.")},
+    {"id": "lease_asset", "title": "租赁物", "prefixes": ("lease.", "asset.", "insurance.")},
+    {"id": "enhancement", "title": "增信措施", "prefixes": ("guarantee.", "enhancement.", "deposit.")},
     {"id": "credit_legal", "title": "征信与涉诉", "prefixes": ("credit.", "legal.", "lawsuit.")},
     {"id": "transaction", "title": "交易结构与还款", "prefixes": ("facility.", "collection.", "repayment.")},
 )