Add perma-ban feature and switch license to MIT
Introduce a permanent-ban flow and update project license to MIT.

• Add a manual GitHub Actions workflow (.github/workflows/manual-package.yml) to build zips for extension and source review with a manual version input.
• Add LICENSE (MIT) and update documentation/metadata to reflect MIT licensing (README, user script header, popup About, package.json license field).
• Implement perma-ban UX and logic: add a "Perma" button to placeholders, styles for the perma button, new convertHiddenToPermaban helper, and wire an onPermaban callback through hide/rehide logic.
• Wire content script to handle permaban actions (doPermaban), persist via updateEntry, update matcher/cache, and show a toast with an option to undo the permaban which restores the result and re-applies blocking.
• Adjust imports to include new helpers (convertHiddenToPermaban, restoreResult) and messaging functions (updateEntry, undoLast).

These changes add a stronger hide mode (permanent ban) and provide tooling to produce manually-versioned release artifacts.