feat(blog): allow members to edit published posts with approval workflow

[RsbhThakur]

Closes #28.

Implements an editorial workflow allowing member authors to stage edits on their published blog posts without immediately modifying live content. Staged updates can be saved incrementally, previewed, withdrawn, or submitted to administrators for review. Administrators receive notifications, can inspect an inline line-by-line visual diff comparing the live post against proposed changes, and can approve or reject revisions with automatic cache invalidation and author notifications.

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Key Changes

1. Data Schema & Access Control

• BlogPost Schema: Added pendingRevision subdocument storing staged revision content (title, content, excerpt, coverImage, coverFocalPoint, tags, updatedAt, submittedAt, submittedBy).
• RBAC: Expanded canEditBlogDraft and exported isBlogAuthor / canAccessBlogEditor so authors can access the editor for their published posts while maintaining strict non-author protection.

2. Member Revision Flow

• PATCH /api/internal/blog/[slug]:
  • Automatically routes published post edits to pendingRevision (staging).
  • Supports requestApproval: true to submit for admin review.
  • Supports cancelApproval: true to withdraw review requests back to draft staging without losing work.
  • Supports DELETE to discard staged revisions and revert to live content.
• UI & Dashboard:
  • Added "Edit Article" pencil button in the public blog header for authors/admins.
  • Enhanced Member Dashboard (/internal/dashboard) with "My Blogs" list, direct edit links, and contextual status badges (published · draft changes saved, published · changes pending approval).

3. Admin Review & Diff Inspector

• POST /api/admin/blog/[slug]/revision: Endpoint supporting approve (atomically applies revision to live fields and clears staging) and reject (discards revision) with cache and Next.js path revalidations.
• Inline Diff Inspector (RevisionDiffViewer):
  • Displays field-by-field comparison for Title, Excerpt, Tags, and Cover Image.
  • Features an inline unified diff viewer showing added (+ green) and deleted (- red) lines with line numbers.
  • Renders the complete BlogEditor directly below for live preview and admin adjustments.

4. Notifications & Audit Logging

• Notifications:
  • Added "blog_revision" to NOTIFICATION_TYPES.
  • Automatically notifies all Heads/Admins upon revision submission.
  • Automatically notifies the author upon approval or rejection.
• Audit Logging: Recorded operations for blog.revision.update, blog.revision.submit, blog.revision.withdraw, blog.revision.approve, and blog.revision.reject.

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Verification & Testing

• Automated Integration Tests:
  • tests/integration/blog-admin.test.ts (approval and rejection flows, cache invalidation, audit trails).
  • tests/integration/blog-member-drafts.test.ts (revision creation, submission, and author RBAC).
  • tests/integration/blog-images.test.ts (author image uploads against published post revisions).
• Typecheck: pnpm typecheck (tsc --noEmit) passes with 0 errors.
• Manual E2E Testing: Verified member staging, review withdrawal, admin diff inspector, live updates, and notification delivery.

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Screenshots

[RsbhThakur]

Usage note for admin: The admin need to go to the edit page of the blog they want to reject/aprove edit requests and on that page they can view the diff and approve/reject the changes.

Also a natural follow up to this PR would be to send notifications to the admins for newly requested changes on blogs and to the authors on the admin's decisions. Opening a seperate issue for it as it is out of scope of the current PR.

All comments addressed