Polish chat UI and wire flue agent env

- Add chat components (header, composer, conversation, message, thinking response, identity)
- Add chat hooks (use-chat-agent, use-chat-composer)
- Add chat lib (constants, transforms, types)
- Wire agent model config through env (provider, name, api, base url, key, context window, max tokens)
- Refresh web styling and routes

packages/env/src/vite-env.d.ts

@@ -1,6 +1,7 @@
 interface ImportMetaEnv {
   readonly [key: string]: string | number | boolean | undefined;
   readonly VITE_CONVEX_SITE_URL: string;
+  readonly VITE_FLUE_URL: string;
   readonly VITE_CONVEX_URL: string;
 }
 

packages/env/src/web.ts

@@ -10,6 +10,7 @@ export const env = createEnv({
   client: {
     VITE_CONVEX_SITE_URL: convexUrlSchema("example.convex.site"),
     VITE_CONVEX_URL: convexUrlSchema("example.convex.cloud"),
+    VITE_FLUE_URL: z.url(),
   },
   clientPrefix: "VITE_",
   emptyStringAsUndefined: true,