feat(moderation): add user-facing reasons for rejected or failed content

Prompt AI models to provide short explanations for rejected content
Store reasons in database and broadcast via WebSocket
Display moderation details in UI for authors and admins

system-wordings.ts

@@ -923,6 +923,7 @@ export const systemWordingMessages = {
         moderationApproved: 'Approved',
         moderationRejected: 'Rejected',
         moderationFailed: 'Review failed',
+        moderationReason: 'Review detail',
         moderationRetry: 'Retry review',
         moderationRetrying: 'Retrying',
         moderationRetryFailed: 'Review retry failed',
@@ -1134,6 +1135,7 @@ export const systemWordingMessages = {
       moderationApproved: 'Approved',
       moderationRejected: 'Rejected',
       moderationFailed: 'Review failed',
+      moderationReason: 'Review detail',
       moderationRetry: 'Retry review',
       moderationRetrying: 'Retrying',
       moderationRetryFailed: 'Review retry failed',
@@ -2181,6 +2183,7 @@ export const systemWordingMessages = {
         moderationApproved: '审核通过',
         moderationRejected: '审核不通过',
         moderationFailed: '审核失败',
+        moderationReason: '审核详情',
         moderationRetry: '重新审核',
         moderationRetrying: '重审中',
         moderationRetryFailed: '重新审核失败',
@@ -2392,6 +2395,7 @@ export const systemWordingMessages = {
       moderationApproved: '审核通过',
       moderationRejected: '审核不通过',
       moderationFailed: '审核失败',
+      moderationReason: '审核详情',
       moderationRetry: '重新审核',
       moderationRetrying: '重审中',
       moderationRetryFailed: '重新审核失败',