fix(core): reduce ollama startup blocking and handle cold starts gracefully

The ensure_ollama() function previously blocked for up to 10 seconds
waiting for Ollama to become reachable after spawning. Cold starts can
take 30-60s, so this often timed out and reported a misleading error.

Now waits only 5 seconds (enough for hot restarts), and if Ollama is
still starting, reports started=true with no error instead of treating
it as a failure. The embed stage runs 60-90s later (after ingestion),
by which time Ollama is ready. The handler log message is updated to
distinguish hot restarts from cold starts still in progress.

src/app/handlers.rs

@@ -1672,8 +1672,10 @@ async fn handle_sync_cmd(
                 "Ollama is not installed — embeddings will be skipped. {}",
                 result.install_hint.as_deref().unwrap_or("")
             );
-        } else if result.started {
+        } else if result.started && result.running {
             tracing::info!("Started ollama serve (was not running)");
+        } else if result.started {
+            tracing::info!("Spawned ollama serve (cold start in progress, should be ready by embed stage)");
         } else if !result.running {
             tracing::warn!(
                 "Failed to start Ollama: {}",