Enhance HTML report dashboard

[Calvin1989]

Summary

• Enhanced the existing HTML report into a zero-dependency dashboard-style report.
• Added severity summary badges and severity filtering.
• Added expandable finding cards with fingerprints.
• Added baseline delta and suppressed findings sections.
• Preserved standalone HTML output without adding runtime dependencies.
• Bumped package version to 2.13.0.

Tests

• python -m pytest
• 98 passed