feat(admin-web): support offline settlement in batch create

When batch creating special deductions:
- Amount empty or 0: auto-switch to offline settlement mode
- Amount > 0: normal deduction mode (requires reason)
- Add hint text in batch create modal for special deduction

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/admin-web/src/app/(dashboard)/pending-actions/page.tsx

@@ -376,7 +376,45 @@ export default function PendingActionsPage() {
     }
 
     let actionParams: Record<string, unknown> | undefined;
-    if (batchFormData.actionParams.trim()) {
+
+    // 特殊扣减的特殊处理
+    if (batchFormData.actionCode === ACTION_CODES.SPECIAL_DEDUCTION) {
+      // 尝试解析已有参数
+      let parsedParams: Record<string, unknown> = {};
+      if (batchFormData.actionParams.trim()) {
+        try {
+          parsedParams = JSON.parse(batchFormData.actionParams);
+        } catch {
+          toast.error('操作参数格式错误，请输入有效的 JSON');
+          return;
+        }
+      }
+
+      const amount = typeof parsedParams.amount === 'number' ? parsedParams.amount : parseFloat(String(parsedParams.amount || '0'));
+      const reason = String(parsedParams.reason || '').trim();
+
+      // 金额为空、NaN 或 <= 0 时，自动切换为全额线下结算模式
+      if (isNaN(amount) || amount <= 0) {
+        actionParams = {
+          amount: 0,
+          reason: reason || '该收益已由用户与上级间线下完成现金收付',
+          createdBy: 'admin',
+          isOfflineSettlement: true,
+        };
+      } else {
+        // 普通模式需要填写原因
+        if (!reason) {
+          toast.error('特殊扣减必须填写原因/备注');
+          return;
+        }
+        actionParams = {
+          amount,
+          reason,
+          createdBy: 'admin',
+          isOfflineSettlement: false,
+        };
+      }
+    } else if (batchFormData.actionParams.trim()) {
       try {
         actionParams = JSON.parse(batchFormData.actionParams);
       } catch {
@@ -904,12 +942,28 @@ export default function PendingActionsPage() {
               </select>
             </div>
 
+            {/* 特殊扣减提示 */}
+            {batchFormData.actionCode === ACTION_CODES.SPECIAL_DEDUCTION && (
+              <div className={styles.pendingActions__modeHint}>
+                <div className={styles.pendingActions__modeHintIcon}>&#9432;</div>
+                <div className={styles.pendingActions__modeHintText}>
+                  <strong>特殊扣减参数说明</strong>
+                  <p>金额为空或0：全额线下结算模式，自动扣减用户所有已结算收益</p>
+                  <p>金额大于0：普通扣减模式，扣减指定金额（需填写原因）</p>
+                </div>
+              </div>
+            )}
+
             <div className={styles.pendingActions__formGroup}>
-              <label>操作参数 (JSON格式，可选)</label>
+              <label>
+                操作参数 (JSON格式{batchFormData.actionCode === ACTION_CODES.SPECIAL_DEDUCTION ? '' : '，可选'})
+              </label>
               <textarea
                 value={batchFormData.actionParams}
                 onChange={(e) => setBatchFormData({ ...batchFormData, actionParams: e.target.value })}
-                placeholder='{"key": "value"}'
+                placeholder={batchFormData.actionCode === ACTION_CODES.SPECIAL_DEDUCTION
+                  ? '{"amount": 0, "reason": "可选备注"}\n金额为0或留空=全额线下结算'
+                  : '{"key": "value"}'}
                 rows={3}
               />
             </div>