feat: public review flow for posts (like artefacts)

- Token-based public review page at /review-post/:token
- Submit for Review button generates shareable link
- External reviewers can approve/reject with comments
- Approval gate prevents skipping review (superadmin override)
- i18n keys for review flow in en + ar

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/i18n/en.json

@@ -889,5 +889,18 @@
   "posts.selectApprovers": "Select approvers...",
   "posts.scheduling": "Scheduling & Assignment",
   "posts.content": "Content",
-  "posts.reject": "Reject"
+  "posts.reject": "Reject",
+  "posts.submittedForReview": "Post submitted for review",
+  "posts.failedSubmitReview": "Failed to submit for review",
+  "posts.reviewLinkCopied": "Review link copied!",
+  "posts.reviewLinkTitle": "Review Link",
+  "posts.awaitingReview": "Awaiting Review",
+  "posts.awaitingReviewDesc": "This post is waiting for external approval.",
+  "posts.approvedBy": "Approved by",
+  "posts.rejectedBy": "Rejected by",
+  "posts.submitting": "Submitting...",
+  "posts.submitForReview": "Submit for Review",
+  "posts.schedulePost": "Schedule Post",
+  "review.postReview": "Post Review",
+  "review.createdBy": "Created by"
 }