fix: correct tojson|safe usage in templates and update validator

- Remove |safe from |tojson in HTML attributes (x-data) - quotes must
  become " for browsers to parse correctly
- Update LANG-002 and LANG-003 architecture rules to document correct
  |tojson usage patterns:
  - HTML attributes: |tojson (no |safe)
  - Script blocks: |tojson|safe
- Fix validator to warn when |tojson|safe is used in x-data (breaks
  HTML attribute parsing)
- Improve code quality across services, APIs, and tests

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

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

models/schema/payment.py

@@ -15,7 +15,6 @@ from typing import Any
 
 from pydantic import BaseModel, Field
 
-
 # ============================================================================
 # PAYMENT CONFIGURATION SCHEMAS
 # ============================================================================
@@ -152,7 +151,9 @@ class PaymentBalanceResponse(BaseModel):
 class RefundRequest(BaseModel):
     """Request model for processing a refund."""
 
-    amount: float | None = Field(None, gt=0, description="Partial refund amount, or None for full refund")
+    amount: float | None = Field(
+        None, gt=0, description="Partial refund amount, or None for full refund"
+    )
     reason: str | None = Field(None, max_length=500)