Fix health check to prevent restart loop

Add missing API key guard for Nebius Chat Completions check.
Now all services properly return 'missing_key' instead of 'error'
when API keys are not configured, preventing Docker health probe
failures and container restart loops.

server/api-health-check.ts

@@ -86,20 +86,28 @@ export async function checkAPIHealth(): Promise<APIHealthStatus[]> {
 
   // Check Nebius Chat Completions (DeepSeek model)
   try {
-    const startTime = Date.now();
-    await nebiusClient.createChatCompletion({
-      model: "deepseek-ai/DeepSeek-R1-0528",
-      messages: [{ role: "user", content: "Hello" }],
-      max_tokens: 5
-    });
-    const responseTime = Date.now() - startTime;
-    
-    results.push({
-      service: 'Nebius Chat (DeepSeek)',
-      status: 'healthy',
-      message: 'Successfully completed test chat with DeepSeek model',
-      responseTime
-    });
+    if (!process.env.NEBIUS_API_KEY) {
+      results.push({
+        service: 'Nebius Chat (DeepSeek)',
+        status: 'missing_key',
+        message: 'NEBIUS_API_KEY environment variable not set'
+      });
+    } else {
+      const startTime = Date.now();
+      await nebiusClient.createChatCompletion({
+        model: "deepseek-ai/DeepSeek-R1-0528",
+        messages: [{ role: "user", content: "Hello" }],
+        max_tokens: 5
+      });
+      const responseTime = Date.now() - startTime;
+      
+      results.push({
+        service: 'Nebius Chat (DeepSeek)',
+        status: 'healthy',
+        message: 'Successfully completed test chat with DeepSeek model',
+        responseTime
+      });
+    }
   } catch (error) {
     results.push({
       service: 'Nebius Chat (DeepSeek)',