chore: Improve test coverage to 80%

[laurigates]

Summary

Current test coverage is approximately 40%. The target should be 80% for robust test coverage.

Current Coverage Report

Module	Coverage
admin.py	66%
models.py	51%
rest.py	0%
views.py	0%
Total	~40%

Areas Needing Coverage

High Priority

• application_evaluator/rest.py - All REST API endpoints need tests
• application_evaluator/views.py - Health check and other views

Medium Priority

• application_evaluator/models.py - Clone methods, CSV import, attachment handling
• application_evaluator/admin.py - Admin actions (duplicate, import, etc.)

Acceptance Criteria

• Add tests for all REST API endpoints
• Add tests for model methods (clone, import, scoring)
• Add tests for admin actions
• Achieve 80% overall coverage
• Update pyproject.toml threshold from 40% to 80%

Notes

• Tests currently require PostgreSQL database
• Consider adding SQLite support for faster unit tests
• May need fixtures for complex test scenarios

Related to #24