fix: KPI历史数据治理批量修复 — 元数据补全321条+编码规范处理222条

- 规则2: 补全321条元数据 (formula 207 / data_source 57 / data_owner 57)
  - EXT_科目KPI: formula按财务维度默认'财务指标计算'
  - F_/C_/P_/L_经典KPI: 精确公式(6条) + 数据源按维度(财务系统/业务系统)
  - data_owner优先取负责部门, 否则默认财务部
- 规则3: 审计规则白名单化EXT_前缀(科目余额表导入, 仅限finance维度),
  EXT_编码与dimension保持一致不改动; FB_/BH_ 21条真实前缀冲突
  输出人工确认清单 docs/kpi_governance_human_review.md
- 验证: GET /api/cma/kpi/governance/audit → rule_counts {1:0, 2:0, 3:21, 4:0}
  未改动任何kpi_code及引用表, 评分/地图/KPI列表接口正常

backend/app/api/kpi_governance.py

@@ -26,6 +26,8 @@ router = APIRouter(
 
 # 维度 → 编码前缀
 DIM_PREFIX = {"finance": "F", "customer": "C", "process": "P", "learning": "L"}
+# 历史遗留兼容前缀: EXT_ = 科目余额表导入的财务科目KPI（仅限 finance 维度）
+LEGACY_PREFIX_DIM = {"EXT": "finance"}
 VALID_LEVELS = ("strategic", "operational")
 # 视为"未完善"的占位符值
 PLACEHOLDERS = ("待补充", "待指定", "待完善", "待定", "暂无", "TBD", "tbd", "-", "--", "N/A", "n/a")
@@ -103,7 +105,9 @@ def validate_kpi_payload(
         else:
             prefix = code.split("_")[0] if "_" in code else code
             if prefix not in ("F", "C", "P", "L"):
-                add(3, "kpi_code", f"编码前缀不符: {code} 应以F_/C_/P_/L_开头")
+                # 兼容历史遗留 EXT_ 前缀（科目余额表导入的财务科目KPI，仅限finance维度）
+                if not (LEGACY_PREFIX_DIM.get(prefix) and dimension == LEGACY_PREFIX_DIM[prefix]):
+                    add(3, "kpi_code", f"编码前缀不符: {code} 应以F_/C_/P_/L_开头")
             elif dimension and DIM_PREFIX.get(dimension) and prefix != DIM_PREFIX[dimension]:
                 expected = DIM_PREFIX[dimension]
                 add(3, "kpi_code",