feat(admin): link city-partner store count; fix benefitUsageRule null string

City partner storeCount jumps to /stores?partnerId=; normalize empty/null text so usage rule is not saved as literal "null.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/dukang-api/src/modules/store/store.service.ts

@@ -28,6 +28,14 @@ function haversineMeters(lat1: number, lng1: number, lat2: number, lng2: number)
   return 2 * R * Math.asin(Math.min(1, Math.sqrt(a)));
 }
 
+/** 选填文案：空 / null / "null" 存库为 null，避免 String(null)==="null" */
+function normalizeOptionalTextField(value: unknown): string | null {
+  if (value == null) return null;
+  const s = String(value).trim();
+  if (!s || /^null$/i.test(s) || /^undefined$/i.test(s)) return null;
+  return s;
+}
+
 function parseOptionalCoord(value: unknown, kind: 'lat' | 'lng' = 'lng'): number | null {
   if (value == null || value === '') return null;
   const n = typeof value === 'number' ? value : Number(value);
@@ -301,9 +309,8 @@ export class StoreService {
     if (introRaw && (introRaw.length < 2 || introRaw.length > 500)) {
       throw new BadRequestException('门店简介须为 2~500 字');
     }
-    const benefitUsageRuleRaw =
-      body.benefitUsageRule != null ? String(body.benefitUsageRule).trim() : '';
-    if (benefitUsageRuleRaw.length > 1000) {
+    const benefitUsageRuleRaw = normalizeOptionalTextField(body.benefitUsageRule);
+    if (benefitUsageRuleRaw && benefitUsageRuleRaw.length > 1000) {
       throw new BadRequestException('好客权益券使用规则最多 1000 字');
     }
 
@@ -325,7 +332,7 @@ export class StoreService {
         district: String(body.district ?? ''),
         address: String(body.address),
         intro: introRaw || null,
-        benefitUsageRule: benefitUsageRuleRaw || null,
+        benefitUsageRule: benefitUsageRuleRaw,
         avgPrice: avgPriceRaw,
         openTime,
         closeTime,
@@ -522,7 +529,9 @@ export class StoreService {
     const address = body.address !== undefined ? String(body.address).trim() : undefined;
     const introRaw = body.intro !== undefined ? String(body.intro).trim() : undefined;
     const benefitUsageRuleRaw =
-      body.benefitUsageRule !== undefined ? String(body.benefitUsageRule).trim() : undefined;
+      body.benefitUsageRule !== undefined
+        ? normalizeOptionalTextField(body.benefitUsageRule)
+        : undefined;
     const latitude =
       body.latitude !== undefined ? parseOptionalCoord(body.latitude, 'lat') : undefined;
     const longitude =
@@ -536,7 +545,7 @@ export class StoreService {
     if (introRaw && (introRaw.length < 2 || introRaw.length > 500)) {
       throw new BadRequestException('门店简介须为 2~500 字');
     }
-    if (benefitUsageRuleRaw !== undefined && benefitUsageRuleRaw.length > 1000) {
+    if (benefitUsageRuleRaw != null && benefitUsageRuleRaw.length > 1000) {
       throw new BadRequestException('好客权益券使用规则最多 1000 字');
     }
     if (
@@ -561,7 +570,7 @@ export class StoreService {
         ...(hasCoordsUpdate ? { latitude, longitude } : {}),
         ...(introRaw !== undefined ? { intro: introRaw || null } : {}),
         ...(benefitUsageRuleRaw !== undefined
-          ? { benefitUsageRule: benefitUsageRuleRaw || null }
+          ? { benefitUsageRule: benefitUsageRuleRaw }
           : {}),
         ...(resubmitAudit
           ? {