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/issue_detail.html

@@ -12,7 +12,7 @@
     <div class="card issue-detail-card">
         <div class="issue-detail-header">
             <span class="issue-number">#{{ issue.number }}</span>
-            <h1 class="issue-detail-title">{{ issue.title }}</h1>
+            <h1 class="issue-detail-title">{{ render_title(issue.title) }}</h1>
             <span class="issue-status {{ issue.state }}">{{ issue.state }}</span>
         </div>
         <div class="issue-meta">
@@ -40,7 +40,7 @@
         </div>
         {% endif %}
 
-        <div class="issue-detail-body rendered-content" data-render>{{ body }}</div>
+        <div class="issue-detail-body rendered-content">{{ render_content(body) }}</div>
     </div>
 
     <section class="comments-section">
@@ -57,7 +57,7 @@
                 <span class="issue-dot">&middot;</span>
                 <span class="issue-date">{{ local_dt(comment.created_at) }}</span>
             </div>
-            <div class="issue-comment-body rendered-content" data-render>{{ comment.body }}</div>
+            <div class="issue-comment-body rendered-content">{{ render_content(comment.body) }}</div>
         </div>
         {% else %}
         <p class="no-comments-msg">No updates yet.</p>