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/dict/bot-dict.ts

@@ -95,6 +95,39 @@ export const BotMessageAuthors = [
 
 export type BotMessageAuthor = (typeof BotMessageAuthors)[number]["value"];
 
+/**
+ * The emoji a message can be reacted with. Kept small and fixed, so the
+ * picker stays a row and every reaction reads the same everywhere.
+ */
+export const BotMessageReactions = [
+    {
+        title: "Like",
+        value: "👍",
+    },
+    {
+        title: "Love",
+        value: "❤️",
+    },
+    {
+        title: "Laugh",
+        value: "😂",
+    },
+    {
+        title: "Surprised",
+        value: "😮",
+    },
+    {
+        title: "Sad",
+        value: "😢",
+    },
+    {
+        title: "Celebrate",
+        value: "🎉",
+    },
+] as const;
+
+export type BotMessageReactionEmoji = (typeof BotMessageReactions)[number]["value"];
+
 export const BotTaskStatuses = [
     {
         title: "Active",