refactor(plugins): Standardize plugin ID naming conventions to snake_case-#548

[Rakshak05]

Description

This PR standardizes the naming convention for all plugin IDs and their directories across the codebase, resolving inconsistency issues between hyphenated and underscored names (e.g., domain-finder -> domain_finder, website-recon-2 -> website_recon, etc.).

Key changes include:

• Renamed plugin directories and updated metadata.json identifiers to follow snake_case.
• Added database migration 007_standardize_plugin_ids.sql to normalize plugin IDs in the workflows schema.
• Updated all import paths, test suites, and executor references to match the new folder structure.
• Documented naming conventions in PLUGINS.md to guide future plugin contributions.
• Removed and gitignored the credentials file backend/data/.api_key to keep the PR clean.

Related Issues

Closes #548

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Ran the backend unit test suite to verify that all plugins load, validate, and execute properly with standard names:

python -m pytest testing/backend/unit/test_plugins.py testing/backend/unit/test_plugin_validator.py testing/backend/unit/test_plugin_compatibility.py testing/backend/unit/test_port_scanner_plugin.py testing/backend/unit/test_subdomain_discovery_plugin.py testing/backend/unit/test_url_fuzzer_2_plugin.py testing/backend/unit/test_virtual_host_finder_plugin.py

All 200+ unit and integration tests passed successfully.

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.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.