fix: add dynamic timeout for document uploads (refs #33)

Document uploads were failing with "timeout of 10000ms exceeded" error
because the global axios client timeout (10s) was too short for
medium-sized files (1-5MB).

Added calculateUploadTimeout() function that calculates timeout based on
file size: 30s base + 10s per MB. This allows uploads to complete on
slower connections while still having reasonable timeout limits.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/features/documents/api/documents.api.ts

@@ -1,6 +1,17 @@
 import { apiClient } from '../../../core/api/client';
 import type { CreateDocumentRequest, DocumentRecord, UpdateDocumentRequest } from '../types/documents.types';
 
+/**
+ * Calculate upload timeout based on file size.
+ * Base: 30 seconds + 10 seconds per MB to accommodate slow connections.
+ */
+function calculateUploadTimeout(file: File): number {
+  const fileSizeMB = file.size / (1024 * 1024);
+  const baseTimeout = 30000; // 30 seconds minimum
+  const perMBTimeout = 10000; // 10 seconds per MB
+  return Math.round(baseTimeout + fileSizeMB * perMBTimeout);
+}
+
 export const documentsApi = {
   async list(params?: { vehicleId?: string; type?: string; expiresBefore?: string }) {
     const res = await apiClient.get<DocumentRecord[]>('/documents', { params });
@@ -26,6 +37,7 @@ export const documentsApi = {
     form.append('file', file);
     const res = await apiClient.post<DocumentRecord>(`/documents/${id}/upload`, form, {
       headers: { 'Content-Type': 'multipart/form-data' },
+      timeout: calculateUploadTimeout(file),
     });
     return res.data;
   },
@@ -34,6 +46,7 @@ export const documentsApi = {
     form.append('file', file);
     const res = await apiClient.post<DocumentRecord>(`/documents/${id}/upload`, form, {
       headers: { 'Content-Type': 'multipart/form-data' },
+      timeout: calculateUploadTimeout(file),
       onUploadProgress: (evt) => {
         if (evt.total) {
           const pct = Math.round((evt.loaded / evt.total) * 100);