feat: implement chat history, theme customization, and password management

- Added chat history persistence for active rooms with auto-cleanup on stream end.
- Overhauled Settings page with user profile, theme color picker, and password change.
- Added backend API for user password updates.
- Integrated flutter_launcher_icons and updated app icon to 'H' logo.
- Fixed 'Duplicate keys' bug in danmaku by using UniqueKey and filtering historical messages.
- Updated version to 1.0.0-beta3.5 and author info.

backend/internal/chat/hub.go

@@ -16,10 +16,11 @@ const (
 )
 
 type Message struct {
-	Type     string `json:"type"` // "chat", "system", "danmaku"
-	Username string `json:"username"`
-	Content  string `json:"content"`
-	RoomID   string `json:"room_id"`
+	Type      string `json:"type"` // "chat", "system", "danmaku"
+	Username  string `json:"username"`
+	Content   string `json:"content"`
+	RoomID    string `json:"room_id"`
+	IsHistory bool   `json:"is_history"`
 }
 
 type Client struct {
@@ -31,19 +32,21 @@ type Client struct {
 }
 
 type Hub struct {
-	rooms      map[string]map[*Client]bool
-	broadcast  chan Message
-	register   chan *Client
-	unregister chan *Client
-	mutex      sync.RWMutex
+	rooms        map[string]map[*Client]bool
+	roomsHistory map[string][]Message
+	broadcast    chan Message
+	register     chan *Client
+	unregister   chan *Client
+	mutex        sync.RWMutex
 }
 
 func NewHub() *Hub {
 	return &Hub{
-		broadcast:  make(chan Message),
-		register:   make(chan *Client),
-		unregister: make(chan *Client),
-		rooms:      make(map[string]map[*Client]bool),
+		broadcast:    make(chan Message),
+		register:     make(chan *Client),
+		unregister:   make(chan *Client),
+		rooms:        make(map[string]map[*Client]bool),
+		roomsHistory: make(map[string][]Message),
 	}
 }
 
@@ -56,6 +59,20 @@ func (h *Hub) Run() {
 				h.rooms[client.RoomID] = make(map[*Client]bool)
 			}
 			h.rooms[client.RoomID][client] = true
+
+			// Send existing history to the newly joined client
+			if history, ok := h.roomsHistory[client.RoomID]; ok {
+				for _, msg := range history {
+					msg.IsHistory = true
+					msgBytes, _ := json.Marshal(msg)
+					// Use select to avoid blocking if client's send channel is full
+					select {
+					case client.Send <- msgBytes:
+					default:
+						// If send fails, we could potentially log or ignore
+					}
+				}
+			}
 			h.mutex.Unlock()
 
 		case client := <-h.unregister:
@@ -64,6 +81,10 @@ func (h *Hub) Run() {
 				if _, ok := rooms[client]; ok {
 					delete(rooms, client)
 					close(client.Send)
+					// We no longer delete the room from h.rooms here if we want history to persist
+					// even if everyone leaves (as long as it's active in DB).
+					// But we should clean up if the room is empty and we want to save memory.
+					// However, the history is what matters.
 					if len(rooms) == 0 {
 						delete(h.rooms, client.RoomID)
 					}
@@ -72,7 +93,16 @@ func (h *Hub) Run() {
 			h.mutex.Unlock()
 
 		case message := <-h.broadcast:
-			h.mutex.RLock()
+			h.mutex.Lock()
+			// Only store "chat" and "danmaku" messages in history
+			if message.Type == "chat" || message.Type == "danmaku" {
+				h.roomsHistory[message.RoomID] = append(h.roomsHistory[message.RoomID], message)
+				// Limit history size to avoid memory leak (e.g., last 100 messages)
+				if len(h.roomsHistory[message.RoomID]) > 100 {
+					h.roomsHistory[message.RoomID] = h.roomsHistory[message.RoomID][1:]
+				}
+			}
+
 			clients := h.rooms[message.RoomID]
 			if clients != nil {
 				msgBytes, _ := json.Marshal(message)
@@ -85,11 +115,18 @@ func (h *Hub) Run() {
 					}
 				}
 			}
-			h.mutex.RUnlock()
+			h.mutex.Unlock()
 		}
 	}
 }
 
+// ClearRoomHistory removes history for a room, should be called when stream ends
+func (h *Hub) ClearRoomHistory(roomID string) {
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+	delete(h.roomsHistory, roomID)
+}
+
 func (h *Hub) RegisterClient(c *Client) {
 	h.register <- c
 }