Add a unique_id field for identifiying conversations (#914)

* Add a unique_id field to the conversation object

- This helps us keep track of the unique identity of the conversation without expose the internal id
- Create three staged migrations in order to first add the field, then add unique values to pre-fill, and then set the unique constraint. Without this, it tries to initialize all the existing conversations with the same ID.

* Parse and utilize the unique_id field in the query parameters of the front-end view

- Handle the unique_id field when creating a new conversation from the home page
- Parse the id field with a lightweight parameter called v in the chat page
- Share page should not be affected, as it uses the public slug

* Fix suggested card category

src/interface/web/app/page.tsx

@@ -138,10 +138,13 @@ function ChatBodyData(props: ChatBodyDataProps) {
             if (message && !processingMessage) {
                 setProcessingMessage(true);
                 try {
-                    const newConversationId = await createNewConversation(selectedAgent || "khoj");
-                    onConversationIdChange?.(newConversationId);
-                    window.location.href = `/chat?conversationId=${newConversationId}`;
+                    const newConversationMetadata = await createNewConversation(
+                        selectedAgent || "khoj",
+                    );
+                    onConversationIdChange?.(newConversationMetadata.conversationId);
+                    window.location.href = `/chat?v=${newConversationMetadata.conversationUniqueId}`;
                     localStorage.setItem("message", message);
+                    localStorage.setItem("conversationId", newConversationMetadata.conversationId);
                     if (image) {
                         localStorage.setItem("image", image);
                     }