docs: document server-side rendering pipeline, response timing middleware, and Telegram pairing API

- Add comprehensive documentation for backend content rendering in AGENTS.md, detailing the new `render_content` and `render_title` Jinja globals built on mistune with media processing, emoji shortcodes, and XSS protection
- Document the `X-Response-Time` header and bottom-left render time indicator in README.md
- Update bot token pricing documentation to clarify fallback vs gateway cost headers
- Add `email_accounts` to soft-delete tables and `idx_users_role` composite index in database schema
- Implement `telegram_pairings` and `telegram_links` table creation with column migration and indexes
- Add `/profile/{username}/telegram` endpoint to docs API with request/unpair actions
- Register `TelegramService` in main.py lifespan and add `response_timing` middleware emitting `X-Response-Time` header
- Introduce `TelegramPairForm` model and `guard_public_host_sync` synchronous host validation function

devplacepy/templates/_comment.html

@@ -18,7 +18,7 @@
             {% set _user = item.author %}{% set _class = "comment-author" %}{% include "_user_link.html" %}
             <span class="comment-time">{{ dt_ago(item.comment.get('created_at')) if item.comment.get('created_at') else item.time_ago }}</span>
         </div>
-        <div class="comment-text rendered-content" data-render data-raw="{{ item.comment['content'] }}">{{ item.comment['content'] }}</div>
+        <div class="comment-text rendered-content" data-raw="{{ item.comment['content'] }}">{{ render_content(item.comment['content']) }}</div>
         {% set attachments = item.get('attachments', []) %}
         {% if attachments %}
         {% include "_attachment_display.html" %}