feat: chat reactions

internal/model/chat.go

@@ -252,6 +252,28 @@ type Message struct {
 	// Attachments is always present (possibly empty) so clients need no nil
 	// check before iterating.
 	Attachments []Attachment `json:"attachments"`
+	// Reactions is always present (possibly empty), same contract as
+	// Attachments — clients render the chip row without a nil check.
+	Reactions []Reaction `json:"reactions"`
+}
+
+// ReactionDetail is one person's reaction, for the "who reacted" list.
+type ReactionDetail struct {
+	User      ChatPeer  `json:"user"`
+	Emoji     string    `json:"emoji"`
+	CreatedAt time.Time `json:"created_at"`
+}
+
+// Reaction is one emoji grouped across the people who chose it.
+//
+// Grouped rather than listed per user: a bubble shows "❤️ 3", and sending the
+// full membership of every reaction would grow with the room.
+type Reaction struct {
+	Emoji string `json:"emoji"`
+	Count int    `json:"count"`
+	// Mine marks the viewer's own choice, so the chip can be highlighted and
+	// tapping it toggles off.
+	Mine bool `json:"mine"`
 }
 
 // Receipts are the conversation-wide delivery cursors used to draw ticks on