fix: update env template to use LANGFUSE_BASE_URL (#1701)

* add LANGFUSE_BASE_URL to .env.template so E2E tests run out-of-the-box

 Closes LFE-10249

* removed deprecated LANGFUSE_HOST from env template

Author: milanagm

.env.template

@@ -1,5 +1,5 @@
 # Langfuse
-LANGFUSE_HOST=http://localhost:3000
+LANGFUSE_BASE_URL=http://localhost:3000
 LANGFUSE_PUBLIC_KEY=pk-lf-1234567890
 LANGFUSE_SECRET_KEY=sk-lf-1234567890