Add application step commands and finalize validation

[davidalecrim1]

Summary

Add CLI support for application step management and finalization, enforce backend validation for final outcome combinations so invalid Offer/Accepted states do not reach the database, and add first-class OpenCode skill installation support.

Type of Change

• Feature
• Fix
• Improvement
• Refactor
• Documentation

Included Changes

Features

• Add applika applications steps list/add/edit/delete and applika applications finalize
• Add JSON output for step listing and finalization, plus applika version
• Add ~/.agents/skills as a built-in applika skill install target for OpenCode

Improvements

• Add explicit --application-id and --step-record-id aliases while keeping positional IDs backward compatible
• Enforce backend finalization rules for Offer plus Accepted and salary_offer
• Expand CLI and backend test coverage for the new flows and guards

Testing

• Unit tests
• Integration tests
• Manual testing
• N/A

Notes

• Backend integration tests could not be run locally in this session because Testcontainers could not reach the Docker daemon.

Checklist

• Self-review completed
• CI passing
• Ready to merge

[italo-gouveia]

LGTM