Implement chat backend and frontend scaffolding

Expanded chat backend with message reply, edit, delete, and reaction support in consumers and models. Updated routing to use chat_id. Added chat-related view stubs. On the frontend, introduced ChatLayout and ChatPage scaffolding, and routed protected routes through ChatLayout.

backend/social/chat/models.py

@@ -47,6 +47,15 @@ class Message(models.Model):
         on_delete=models.CASCADE,
         related_name='sent_messages'
     )
+
+    #odpověď na jinou zprávu
+    reply_to = models.ForeignKey(
+        'self',
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name='replies'
+    )
     
     content = models.TextField(blank=True)