Comment out problematic component-to-container relationship

Temporarily comment out the @c4-uses relationship from Data Validation
Layer component to Database Layer container. This relationship was
causing Structurizr DSL errors because components shouldn't have
relationships to sibling containers of their parent.

The relationship may be revisited later to determine if it should be
restructured or removed entirely.

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

Author: christosm-dev

app/models.py

@@ -77,7 +77,7 @@
 SYSTEM INTERACTIONS
 -------------------
 @c4-used-by: API Application - "Validates requests and formats responses"
-@c4-uses: Database Layer - "Serializes ORM objects to API responses"
+# @c4-uses: Database Layer - "Serializes ORM objects to API responses"
 
 ERROR HANDLING
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