refactor: remove PullPush.io, use Reddit RSS as primary data source

PullPush.io index was frequently stale/unavailable. Reddit RSS/Atom feeds
work reliably from datacenter IPs (Hostinger) where .json gets 403.

- RSS is now the primary source for post fetching
- .json endpoints kept as fallback for posts and sole source for comments
- Deleted class-pull-push-client.php
- Updated admin UI, test connection handler, docs, and ARCHITECTURE.md

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

prautoblogger.php

@@ -8,7 +8,7 @@ declare(strict_types=1);
  * Plugin Name:       PRAutoBlogger
  * Plugin URI:        https://peptiderepo.com/prautoblogger
  * Description:       Monitors social media for trending topics, generates SEO-friendly blog posts using AI, and publishes them on a daily schedule with full cost tracking and self-improvement metrics.
- * Version:           0.2.0
+ * Version:           0.2.1
  * Requires at least: 6.0
  * Requires PHP:      7.4
  * Author:            PeptideRepo