Update LLM URL and warn if LLM not configured

Updates the `LLM_URL` in the project plan and `.env.example` to the
correct value.
Also, adds a warning in `main.rs` to inform the user if the LLM is not
configured, which effectively disables the 'Fall abschließen' feature.

server/src/main.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 use tokio::net::TcpListener;
 use tower_http::limit::RequestBodyLimitLayer;
 use tower_http::trace::TraceLayer;
-use tracing::info;
+use tracing::{info, warn};
 use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::util::SubscriberInitExt;
 use tracing_subscriber::EnvFilter;
@@ -40,6 +40,14 @@ async fn main() {
         )
         .init();
 
+    // Surface configuration gaps that silently disable features.
+    if !config.llm_configured() {
+        warn!(
+            "LLM not configured — 'Fall abschließen' is disabled. \
+             Set LLM_URL, LLM_API_KEY and LLM_MODEL in .env to enable."
+        );
+    }
+
     // Shared HTTP client for both downstream pipelines.
     let http_client = reqwest::Client::builder()
         .build()