Make conversations optionally shareable (#712)

* Make conversations optionally shareable

- Shared conversations are viewable by anyone, without a login wall
- Can share a conversation from the three dot menu
- Add a new model for Public Conversation
- The rationale for a separate model is that public and private conversations have different assumptions. Separating them reduces some of the code specificity on our server-side code and allows us for easier interpretation and stricter security. Separating the data model makes it harder to accidentally view something that was meant to be private
- Add a new, read-only view for public conversations

src/interface/desktop/chat.html

@@ -1075,11 +1075,12 @@
                                 threeDotMenu.appendChild(conversationMenu);
 
                                 let deleteButton = document.createElement('button');
+                                deleteButton.type = "button";
                                 deleteButton.innerHTML = "Delete";
                                 deleteButton.classList.add("delete-conversation-button");
                                 deleteButton.classList.add("three-dot-menu-button-item");
-                                deleteButton.addEventListener('click', function() {
-                                    // Ask for confirmation before deleting chat session
+                                deleteButton.addEventListener('click', function(event) {
+                                    event.preventDefault();
                                     let confirmation = confirm('Are you sure you want to delete this chat session?');
                                     if (!confirmation) return;
                                     let deleteURL = `/api/chat/history?client=web&conversation_id=${incomingConversationId}`;
@@ -1927,6 +1928,7 @@
             text-align: left;
             display: flex;
             position: relative;
+            margin: 0 8px;
         }
 
         .three-dot-menu {