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/routers/profile/index.py

@@ -262,6 +262,11 @@ async def profile_page(
         if is_owner
         else None
     )
+    from devplacepy.services.telegram import store as telegram_store
+
+    telegram_paired = (
+        telegram_store.is_paired(profile_user["uid"]) if is_owner else False
+    )
     profile_is_admin = profile_user.get("role") == "Admin"
     ai_quota = (
         _ai_quota(
@@ -349,6 +354,7 @@ async def profile_page(
             "ai_modifier_enabled": ai_modifier_enabled,
             "ai_modifier_sync": ai_modifier_sync,
             "ai_modifier_prompt": ai_modifier_prompt,
+            "telegram_paired": telegram_paired,
             "can_manage_customization": can_manage_customization,
             "cust_disable_global": customization_prefs["disable_global"],
             "cust_disable_pagetype": customization_prefs["disable_pagetype"],