test: add contract and parser coverage for website-recon-2

[mythri2405]

Description

Adds contract and parser coverage for the website-recon-2 plugin.

Changes

• Added metadata contract tests for website-recon-2
• Added plugin validation tests using PluginMetadataValidator
• Added command rendering tests through PluginManager
• Added parser contract tests with deterministic fixture data
• Added assertions for parser severity classification
• Added empty-output handling tests
• Added metadata preservation checks for parsed findings

This improves coverage for the plugin and helps detect regressions in metadata validation, command rendering, and parser normalization.

Related Issues

Closes #519

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Executed the plugin-specific test suite:

python -m pytest testing/backend/test_website_recon_2_plugin.py -q

The tests verify:

• Metadata loading and validation
• Plugin command rendering
• Plugin loading through PluginManager
• Parser output contract
• Severity classification
• Empty output handling
• Metadata preservation

Checklist

• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.