Fix: Add _open() and path() methods to TenantAwareFileSystemStorage

Critical fix for Celery photo processing. The storage class now correctly
handles file reading operations by automatically adding tenant_id prefix
when opening files.

Problems fixed:
- Celery tasks could not open image files from storage
- PIL/Pillow couldn't locate files in tenant-specific directories
- temp file deletion was failing due to path validation

Changes:
- Added _open() method to add tenant_id prefix when opening files
- Added path() method to convert relative paths to full filesystem paths
- Updated delete() method to handle paths with or without tenant prefix
- All methods include security checks to prevent cross-tenant access

Testing:
- All 5 existing tests pass
- Verified photo processing task works end-to-end:
  * Reads temp image file from disk
  * Processes and creates all image versions
  * Saves processed files to tenant-specific directory
  * Cleans up temporary files correctly
- Files correctly stored in: media/tenants/{tenant_id}/products/{product_id}/{photo_id}/

🤖 Generated with Claude Code

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

myproject/pos/templates/pos/terminal.html

@@ -37,10 +37,10 @@
     <!-- Right Panel (4/12) - Fixed -->
     <div class="col-md-4">
       <div class="right-panel-fixed d-flex flex-column">
-        <!-- Информация о складе -->
-        {% if current_warehouse %}
+        <!-- Информация о складе (всегда показываем блок для фиксированной позиции) -->
         <div class="card mb-2">
           <div class="card-body py-2 px-3 d-flex justify-content-between align-items-center">
+            {% if current_warehouse %}
             <div>
               <small class="text-muted d-block" style="font-size: 0.75rem;">Склад:</small>
               <strong style="font-size: 0.95rem;">{{ current_warehouse.name }}</strong>
@@ -48,9 +48,14 @@
             <button class="btn btn-sm btn-outline-secondary" id="changeWarehouseBtn" style="font-size: 0.75rem;">
               <i class="bi bi-arrow-left-right"></i> Сменить
             </button>
+            {% else %}
+            <div class="text-danger">
+              <small class="d-block" style="font-size: 0.75rem;">Склад:</small>
+              <strong style="font-size: 0.95rem;"><i class="bi bi-exclamation-triangle me-1"></i>Не выбран</strong>
+            </div>
+            {% endif %}
           </div>
         </div>
-        {% endif %}
         
         <!-- Cart Panel -->
         <div class="card mb-2 flex-grow-1" style="min-height: 0;">