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/saved.html

@@ -10,7 +10,7 @@
         {% for item in items %}
         <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-title">{{ render_title(item.title) }}</span>
             <span class="saved-item-time">{{ dt_ago(item.created_at) if item.created_at else item.time_ago }}</span>
         </a>
         {% else %}