Fix large file preview and download issues

- Add persistent Docker volume for file storage to fix 404 download errors
- Set FILE_STORAGE_PATH env var in Dockerfile and docker-compose.yml
- Increase thumbnail generation limit from 500KB to 10MB for images
- Remove encodeURIComponent from file download URL to prevent path encoding

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

backend/Dockerfile

@@ -28,6 +28,9 @@ COPY reference_docs/ ./reference_docs/
 # Set reference docs path for container
 ENV REFERENCE_DOCS_PATH=/app/reference_docs
 
+# Set file storage path for container
+ENV FILE_STORAGE_PATH=/app/storage
+
 EXPOSE 8000
 
 CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]

backend/app/websocket/handlers.py

@@ -148,9 +148,9 @@ async def handle_analyze_message(
                         file_type=file_type,
                     )
 
-                    # Generate thumbnail for small files
+                    # Generate thumbnail for images up to 10MB (data URLs are ~33% larger than binary)
                     thumbnail_url = None
-                    if len(file_data) < 500000:  # < 500KB
+                    if len(file_data) < 10000000 and file_type.startswith('image/'):
                         thumbnail_url = await storage_service.generate_thumbnail_data_url(file_data, file_type)
 
                     # Save proof and version

docker-compose.yml

@@ -29,6 +29,9 @@ services:
       - HOST=0.0.0.0
       - PORT=8000
       - DATABASE_URL=postgresql+asyncpg://${POSTGRES_USER:-modcomms}:${POSTGRES_PASSWORD:-modcomms_dev}@postgres:5432/${POSTGRES_DB:-modcomms}
+      - FILE_STORAGE_PATH=/app/storage
+    volumes:
+      - file_storage:/app/storage
     depends_on:
       postgres:
         condition: service_healthy
@@ -42,3 +45,4 @@ services:
 
 volumes:
   postgres_data:
+  file_storage:

frontend/services/apiService.ts

@@ -184,7 +184,7 @@ class ApiService {
 
     async getFile(storageKey: string): Promise<File> {
         const headers = await this.getHeaders();
-        const response = await fetch(`${API_URL}/api/files/${encodeURIComponent(storageKey)}`, { headers });
+        const response = await fetch(`${API_URL}/api/files/${storageKey}`, { headers });
         if (!response.ok) {
             throw new Error(`Failed to fetch file: HTTP ${response.status}`);
         }