docs: add comprehensive documentation for today's work

Technical Documentation:
- docs/development/architecture-fixes-2026-01.md: Complete guide to
  all architecture validation fixes (62 -> 0 errors)

User Guides:
- docs/guides/email-templates.md: How-to guide for vendors and admins
  to use the email template customization system

Implementation Docs:
- docs/implementation/password-reset-implementation.md: Technical
  documentation for the password reset feature
- Updated email-templates-architecture.md with EmailTemplateService
  documentation and related links

Bugfix:
- Fixed TemplateListItem Pydantic model to match service output
  (languages vs available_languages field name)

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

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

app/api/v1/admin/email_templates.py

@@ -63,9 +63,11 @@ class TemplateListItem(BaseModel):
 
     code: str
     name: str
-    description: str
+    description: str | None = None
     category: str
-    available_languages: list[str]
+    languages: list[str]  # Matches service output field name
+    is_platform_only: bool = False
+    variables: list[str] = []
 
     class Config:
         from_attributes = True