fix(telegram): support card — text_mention name, no command/dead link

The topic info card built the profile link as `tg://user?id=`, which
clients render as dead text for a user they don't already know (the
test-vs-prod difference an operator saw), and it put the raw display
name through HTML — so a name starting with "/" was auto-detected as a
tappable bot command that fired when tapped.

Render the card with message entities instead: the display name is
covered by a `text_mention` entity (the reliable way to mention a
username-less user the bot has already seen — it messaged the bot),
which links the profile AND, because the name sits inside an entity,
suppresses the "/command" and "@mention" auto-detection on it. Drop the
HTML parse mode and the tg:// link. Entity offsets are UTF-16.

docs/ARCHITECTURE.md

@@ -1204,8 +1204,10 @@ migration.
 **Telegram support relay.** Separate from the in-app Feedback above, the bot offers a direct
 support channel for users who message it on Telegram. Any message other than `/start` is relayed
 into a private **forum supergroup** (`TELEGRAM_SUPPORT_CHAT_ID`): a user's first message opens a
-dedicated **forum topic** whose first message is an info card (name, @username, language, premium,
-id, profile deep-link) carrying a Block/Unblock toggle and a Clear button; every message is then
+dedicated **forum topic** whose first message is an info card (the name is a tappable profile
+mention via a `text_mention` entity — which also keeps a name beginning with `/` from being read as
+a command — plus @username, language, premium, id) carrying a Block/Unblock toggle and a Clear
+button; every message is then
 copied into that topic (`copyMessage`, so any content — text, media, voice, files — carries over).
 Any **administrator** of the support chat who writes in a user's topic has their message copied
 back to that user; non-admins and the bot's own posts are ignored (the loop guard). Block drops the