perf: add select narrowing to llm_calls.findUnique on detail page

Exclude 8 unused columns from the llm_calls detail page query,
including large JSON blobs (messages, parsed_response, context) and
unused scalar fields (max_tokens, retry_count, user_id, python_version,
is_async). This reduces payload size from the database for every
LLM call detail page view.

js/cf-webapp/src/app/observability/llm-call/[id]/page.tsx

@@ -28,6 +28,30 @@ export default async function LLMCallDetailPage(props: LLMCallDetailPageProps) {
   const [llmCall, relatedErrors] = await Promise.all([
     prisma.llm_calls.findUnique({
       where: { id: params.id },
+      select: {
+        id: true,
+        trace_id: true,
+        call_type: true,
+        model_name: true,
+        system_prompt: true,
+        user_prompt: true,
+        temperature: true,
+        n_candidates: true,
+        raw_response: true,
+        prompt_tokens: true,
+        completion_tokens: true,
+        total_tokens: true,
+        llm_cost: true,
+        latency_ms: true,
+        status: true,
+        error_type: true,
+        error_message: true,
+        parsing_status: true,
+        candidates_generated: true,
+        candidates_valid: true,
+        parsing_errors: true,
+        created_at: true,
+      },
     }),
     prisma.optimization_errors.findMany({
       where: { llm_call_id: params.id },