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.

frontend/lib/pages/player_page.dart

@@ -62,7 +62,7 @@ class _PlayerPageState extends State<PlayerPage> {
       if (mounted) {
         setState(() {
           _messages.insert(0, msg);
-          if (msg.type == "chat" || msg.type == "danmaku") {
+          if (!msg.isHistory && (msg.type == "chat" || msg.type == "danmaku")) {
             _addDanmaku(msg.content);
           }
         });
@@ -71,15 +71,15 @@ class _PlayerPageState extends State<PlayerPage> {
   }
 
   void _addDanmaku(String text) {
-    final id = DateTime.now().millisecondsSinceEpoch;
-    final top = 20.0 + (id % 6) * 30.0; 
+    final key = UniqueKey();
+    final top = 20.0 + (DateTime.now().millisecondsSinceEpoch % 6) * 30.0; 
     
     final danmaku = _DanmakuItem(
-      key: ValueKey(id),
+      key: key,
       text: text,
       top: top,
       onFinished: () {
-        if (mounted) setState(() => _danmakus.removeWhere((w) => w.key == ValueKey(id)));
+        if (mounted) setState(() => _danmakus.removeWhere((w) => w.key == key));
       },
     );