Add our first view via Next.js for Agents (#817)

Initialize our migration to use Next.js for front-end views via Agents. This includes setup for getting authenticated users, reading in available agents, setting up a pop-up modal when you're clicking on an agent, and allowing users to start new conversations with agents.

Best attempt at an in-place migration, though there are some noticeable differences.

Also adds view for chat that are not being used, but in experimental phase.

src/interface/web/app/components/chatHistory/chatHistory.module.css

@@ -0,0 +1,12 @@
+div.chatHistory {
+    display: flex;
+    flex-direction: column;
+    height: 100%;
+}
+
+div.chatLayout {
+    height: 80vh;
+    overflow-y: auto;
+    /* width: 80%; */
+    margin: 0 auto;
+}