feat(monotemplate): add DI skill for Inversify container wiring

[firstloop-jake]

Summary

• Adds new monotemplate:di skill documenting the Inversify v7 dependency injection pattern
• Covers injectable decorators, binding registration, resolution, symbol tokens, simulated auth gating, and a new-entity checklist
• Ensures Claude correctly wires repositories, controllers, and services into the DI container

Closes #21

Test plan

• Install plugin and verify monotemplate:di skill is discoverable
• Trigger skill by asking Claude to add a new repository or controller
• Verify Claude follows the documented patterns (decorators, binding order, container.get)

🤖 Generated with Claude Code