feat: add backup CLI commands, AI correction/modifier services, and timezone-aware date display

- Add `devplace backups` CLI subcommands (list, run, prune, clear) with job enqueueing and orphan cleanup
- Introduce `BACKUPS_DIR` and `BACKUP_STAGING_DIR` config paths for backup storage
- Implement `schedule_correction` and `schedule_modification` calls in content creation, comment creation, and comment editing flows
- Add `DEFAULT_CORRECTION_PROMPT` and `DEFAULT_MODIFIER_PROMPT` config constants for AI content processing
- Document timezone-aware date display using `local_dt`/`dt_ago` Jinja globals with client-side `Intl` localization
- Update README with AI content correction/modifier support in direct messages via `@ai` inline instructions
- Add `track_action(user["uid"], "vote")` call on upvote in `apply_vote`

devplacepy/templates/saved.html

@@ -11,7 +11,7 @@
         <a href="{{ item.url }}" class="saved-item">
             <span class="saved-type badge">{{ item.type_label }}</span>
             <span class="saved-item-title">{{ item.title }}</span>
-            <span class="saved-item-time">{{ item.time_ago }}</span>
+            <span class="saved-item-time">{{ dt_ago(item.created_at) if item.created_at else item.time_ago }}</span>
         </a>
         {% else %}
         <div class="empty-state">Nothing saved yet. Use the Save button on posts, gists, projects and news.</div>