Revert SSE streaming for PDF import, use synchronous flow

SSE streaming added unnecessary complexity and latency due to
buffering issues across Node.js event loop, Nginx proxy, and
Docker layers. Reverted to a simple synchronous request/response
for PDF conversion. Kept extractLlmErrorMessage for user-friendly
LLM errors, lazy-loaded pdf-parse, and extended Nginx timeout.

Dockerfile.backend

@@ -30,6 +30,7 @@ ENV NODE_ENV=production
 COPY --from=build /app/backend/dist ./dist
 COPY --from=build /app/backend/package.json ./package.json
 COPY --from=build /app/node_modules ./node_modules
+COPY --from=build /app/backend/node_modules/ ./node_modules/
 COPY backend/.env .env
 
 EXPOSE 3000

backend/src/services/pdfToStatement.ts

@@ -108,6 +108,7 @@ export async function convertPdfToStatement(
   const openai = new OpenAI({
     apiKey: config.llmApiKey,
     ...(config.llmApiBaseUrl && { baseURL: config.llmApiBaseUrl }),
+    timeout: 5 * 60 * 1000,
   });
 
   try {
@@ -119,7 +120,6 @@ export async function convertPdfToStatement(
       ],
       temperature: 0,
       max_tokens: 32768,
-      response_format: { type: 'json_object' },
     });
 
     const content = completion.choices[0]?.message?.content?.trim();
@@ -159,7 +159,21 @@ export async function convertPdfToStatement(
     return {
       status: 502,
       error: 'BAD_GATEWAY',
-      message: 'Временная ошибка конвертации',
+      message: extractLlmErrorMessage(err),
     };
   }
 }
+
+function extractLlmErrorMessage(err: unknown): string {
+  const raw = String(
+    (err as Record<string, unknown>)?.message ??
+    (err as Record<string, Record<string, unknown>>)?.error?.message ?? '',
+  );
+  if (/context.length|n_ctx|too.many.tokens|maximum.context/i.test(raw)) {
+    return 'PDF-файл слишком большой для обработки. Попробуйте файл с меньшим количеством операций или используйте модель с большим контекстным окном.';
+  }
+  if (/timeout|timed?\s*out|ETIMEDOUT|ECONNREFUSED/i.test(raw)) {
+    return 'LLM-сервер не отвечает. Проверьте, что сервер запущен и доступен.';
+  }
+  return 'Временная ошибка конвертации';
+}

frontend/nginx.conf

@@ -3,6 +3,20 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
+    # Import endpoint — long timeout for LLM processing
+    location /api/import {
+        proxy_pass http://family-budget-backend:3000;
+        proxy_http_version 1.1;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_cookie_path / /;
+        proxy_connect_timeout 5s;
+        proxy_read_timeout 600s;
+        client_max_body_size 15m;
+    }
+
     # API — проксируем на backend (сервис из docker-compose)
     location /api {
         proxy_pass http://family-budget-backend:3000;