refactor: backend standardization (service layer, validation, route splitting) + image cache and Scryfall API fixes

code/web/validation/__init__.py

@@ -0,0 +1,13 @@
+"""Validation package for web application.
+
+Provides centralized validation using Pydantic models and custom validators
+for all web route inputs and business logic validation.
+"""
+from __future__ import annotations
+
+__all__ = [
+    "models",
+    "validators", 
+    "card_names",
+    "messages",
+]