chore: cleanup dead code and unused files

Deleted 7 unused frontend components (ChatBubble, PetZone, Live2DCat,
BackgroundScene, Clock, Toolbar, types/index.ts).
Deleted unused backend: whisper_stream.py, empty models/ and routers/ dirs.
Removed dead code: Message interface, messages/micError/sendText/addMessage,
conversation_text handler, 3 unused memory.py methods.
Fixed task persistence bug: added 'tasks' to DEFAULT_PREFERENCES.
Stale comment in Live2DStage updated.

backend/services/memory.py

@@ -134,57 +134,12 @@ class KiraMemory:
 
         return "\n\n---\n### What Kira remembers:" + "".join(parts)
 
-    def store_messages(
-        self,
-        user_message: str,
-        kira_message: str,
-    ) -> None:
-        """Store a conversation exchange in Honcho."""
-        if not self.enabled or not self._session:
-            return
-
-        try:
-            messages = []
-            if self._user_peer:
-                messages.append(
-                    self._user_peer.message(user_message)
-                )
-            if self._kira_peer:
-                messages.append(
-                    self._kira_peer.message(kira_message)
-                )
-
-            if messages:
-                self._session.add_messages(messages)
-                logger.debug("Stored conversation exchange in Honcho")
-        except Exception as e:
-            logger.warning(f"Failed to store messages: {e}")
-
-    def store_user_message(self, text: str) -> None:
-        """Store a single user message."""
-        if not self.enabled or not self._session or not self._user_peer:
-            return
-        try:
-            self._session.add_messages([self._user_peer.message(text)])
-        except Exception as e:
-            logger.warning(f"Failed to store user message: {e}")
-
-    def store_kira_message(self, text: str) -> None:
-        """Store a single Kira message."""
-        if not self.enabled or not self._session or not self._kira_peer:
-            return
-        try:
-            self._session.add_messages([self._kira_peer.message(text)])
-        except Exception as e:
-            logger.warning(f"Failed to store Kira message: {e}")
-
-    # ─── User preferences (stored in Honcho peer metadata) ───
-
     DEFAULT_PREFERENCES: dict[str, str] = {
         "name": "",
         "scene": "cozy-room",
         "outfit": "cozy-hoodie",
         "accessory": "",
+        "tasks": "[]",
     }
 
     def get_user_preferences(self, user_id: str) -> dict[str, str]: