fix(skills): remove phantom resource references and fix CoC links (#447)

Remove references to non-existent resource files (references/, assets/,
scripts/, examples/) from 115 skill SKILL.md files. These sections
pointed to directories and files that were never created, causing
confusion when users install skills.

Also fix broken Code of Conduct links in issue templates to use
absolute GitHub URLs instead of relative paths that 404.

plugins/backend-development/skills/architecture-patterns/SKILL.md

@@ -464,31 +464,3 @@ class OrderRepository:
         await self._publish_events(order._events)
         order._events.clear()
 ```
-
-## Resources
-
-- **references/clean-architecture-guide.md**: Detailed layer breakdown
-- **references/hexagonal-architecture-guide.md**: Ports and adapters patterns
-- **references/ddd-tactical-patterns.md**: Entities, value objects, aggregates
-- **assets/clean-architecture-template/**: Complete project structure
-- **assets/ddd-examples/**: Domain modeling examples
-
-## Best Practices
-
-1. **Dependency Rule**: Dependencies always point inward
-2. **Interface Segregation**: Small, focused interfaces
-3. **Business Logic in Domain**: Keep frameworks out of core
-4. **Test Independence**: Core testable without infrastructure
-5. **Bounded Contexts**: Clear domain boundaries
-6. **Ubiquitous Language**: Consistent terminology
-7. **Thin Controllers**: Delegate to use cases
-8. **Rich Domain Models**: Behavior with data
-
-## Common Pitfalls
-
-- **Anemic Domain**: Entities with only data, no behavior
-- **Framework Coupling**: Business logic depends on frameworks
-- **Fat Controllers**: Business logic in controllers
-- **Repository Leakage**: Exposing ORM objects
-- **Missing Abstractions**: Concrete dependencies in core
-- **Over-Engineering**: Clean architecture for simple CRUD