test(plugins): add parser and contract coverage for google-dorking (#498)

[Ayushi-hi]

Related Issues

Closes #498

Type of Change

• New test coverage (non-breaking)

Summary

Adds backend test coverage for the google-dorking plugin which had
no direct fixture-based tests. The new test file covers:

• metadata.json contract validation
• plugin loading via PluginManager
• command rendering with target substitution
• dork query pattern assertions
• parser output normalization (findings, count, items)
• severity classification (info vs low)
• edge cases: empty input, 200-line cap, raw_line metadata

How Has This Been Tested?

• 22 passed locally under pytest testing/backend -q

Checklist

• Tests reference google-dorking explicitly
• Metadata loads through current validation path
• Parser output asserted with stable fixture
• No plugin functionality modified

[utksh1]

Reviewed. Focused plugin parser/contract coverage with green checks.