feat: stream PDF import progress via SSE with global progress bar

Replace the synchronous PDF import with Server-Sent Events streaming
between the backend (LLM) and the browser. The user can now close the
import modal and continue working while the conversion runs — a fixed
progress bar in the Layout shows real-time stage and percentage.

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 {
@@ -130,29 +131,7 @@ export async function convertPdfToStatement(
       };
     }
 
-    const jsonMatch = content.match(/\{[\s\S]*\}/);
-    const jsonStr = jsonMatch ? jsonMatch[0] : content;
-    let parsed: unknown;
-    try {
-      parsed = JSON.parse(jsonStr);
-    } catch {
-      return {
-        status: 422,
-        error: 'VALIDATION_ERROR',
-        message: 'Результат конвертации не является валидным JSON',
-      };
-    }
-
-    const data = parsed as Record<string, unknown>;
-    if (data.schemaVersion !== '1.0') {
-      return {
-        status: 422,
-        error: 'VALIDATION_ERROR',
-        message: 'Результат конвертации не соответствует схеме 1.0',
-      };
-    }
-
-    return parsed as StatementFile;
+    return parseConversionResult(content);
   } catch (err) {
     console.error('LLM conversion error:', err);
     return {
@@ -162,3 +141,125 @@ export async function convertPdfToStatement(
     };
   }
 }
+
+export type ProgressStage = 'pdf' | 'llm' | 'import';
+export type OnProgress = (stage: ProgressStage, progress: number, message: string) => void;
+
+const EXPECTED_CHARS = 15_000;
+
+export async function convertPdfToStatementStreaming(
+  buffer: Buffer,
+  onProgress: OnProgress,
+): Promise<StatementFile | PdfConversionError> {
+  if (!config.llmApiKey || config.llmApiKey.trim() === '') {
+    return {
+      status: 503,
+      error: 'SERVICE_UNAVAILABLE',
+      message: 'Конвертация PDF недоступна: не задан LLM_API_KEY',
+    };
+  }
+
+  onProgress('pdf', 2, 'Извлечение текста из PDF...');
+
+  let text: string;
+  try {
+    const result = await getPdfParse()(buffer);
+    text = result.text || '';
+  } catch (err) {
+    console.error('PDF extraction error:', err);
+    return {
+      status: 400,
+      error: 'BAD_REQUEST',
+      message: 'Не удалось обработать PDF-файл',
+    };
+  }
+
+  if (!text || text.trim().length === 0) {
+    return {
+      status: 400,
+      error: 'BAD_REQUEST',
+      message: 'Не удалось извлечь текст из PDF',
+    };
+  }
+
+  onProgress('pdf', 8, 'Текст извлечён, отправка в LLM...');
+
+  const openai = new OpenAI({
+    apiKey: config.llmApiKey,
+    ...(config.llmApiBaseUrl && { baseURL: config.llmApiBaseUrl }),
+    timeout: 5 * 60 * 1000,
+  });
+
+  try {
+    const stream = await openai.chat.completions.create({
+      model: config.llmModel,
+      messages: [
+        { role: 'system', content: PDF2JSON_PROMPT },
+        { role: 'user', content: `Текст выписки:\n\n${text}` },
+      ],
+      temperature: 0,
+      max_tokens: 32768,
+      stream: true,
+    });
+
+    let accumulated = '';
+    let charsReceived = 0;
+
+    for await (const chunk of stream) {
+      const delta = chunk.choices[0]?.delta?.content;
+      if (delta) {
+        accumulated += delta;
+        charsReceived += delta.length;
+        const llmProgress = Math.min(
+          85,
+          Math.round((charsReceived / EXPECTED_CHARS) * 75 + 10),
+        );
+        onProgress('llm', llmProgress, 'Конвертация через LLM...');
+      }
+    }
+
+    const content = accumulated.trim();
+    if (!content) {
+      return {
+        status: 422,
+        error: 'VALIDATION_ERROR',
+        message: 'Результат конвертации пуст',
+      };
+    }
+
+    return parseConversionResult(content);
+  } catch (err) {
+    console.error('LLM streaming error:', err);
+    return {
+      status: 502,
+      error: 'BAD_GATEWAY',
+      message: 'Временная ошибка конвертации',
+    };
+  }
+}
+
+function parseConversionResult(content: string): StatementFile | PdfConversionError {
+  const jsonMatch = content.match(/\{[\s\S]*\}/);
+  const jsonStr = jsonMatch ? jsonMatch[0] : content;
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(jsonStr);
+  } catch {
+    return {
+      status: 422,
+      error: 'VALIDATION_ERROR',
+      message: 'Результат конвертации не является валидным JSON',
+    };
+  }
+
+  const data = parsed as Record<string, unknown>;
+  if (data.schemaVersion !== '1.0') {
+    return {
+      status: 422,
+      error: 'VALIDATION_ERROR',
+      message: 'Результат конвертации не соответствует схеме 1.0',
+    };
+  }
+
+  return parsed as StatementFile;
+}