Add replies and emoji reactions to chat messages

Every message has a row under it to reply or react. Replying quotes the
message above the composer, and the sent message stores
reply_to_message_id (a plain id, not a foreign key, so deleting the
quoted message only drops the quote). send-message accepts a quote from
any session of the same conversation, so a rollover or a thread that
moved on still sends; the conversation drops a picked quote when its
session changes. The bot reads the quote as "[Replying to ...]" before
the user's turn, file-only replies included, and relayed messages carry
it too.

Reactions are a fixed set (BotMessageReactions) in
bot_message_reactions, one per message, emoji and user or bot. Users
toggle their own through api/admin/bots/react-message, and every bot
gets react_to_message for the session it answers (the user's latest
message by default). Both push the fresh list as server:bot-reaction,
with mine worked out for the session's user.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/functions/backend/db/bot-sessions/grab-conversation-props.ts

@@ -67,7 +67,7 @@ export default async function grabConversationProps({
      * shows its pick.
      */
     const [bot_messages, bot_harness_overview, bot_computers, bot_task, bot_extensions, transcription, speech] = await Promise.all([
-        grabBotMessages({ session_id: session.id! }),
+        grabBotMessages({ session_id: session.id!, user_id }),
         (bot.kind == "coordinator" && !scope
             ? grabHarnessOverview().then(({ harnesses }) => ({ harnesses }))
             : grabBotHarnessOverview({