Popup dark mode

• The popup (and blocked page) now supports dark mode with a manual Light / Dark theme
  toggle, letting you switch independent of your OS setting.
• Your theme choice is saved and applied before the first paint, so there's no flash on
  open.

Popup content refresh

• Updated the popup's layout and content for a cleaner, more polished look and improved
  readability in both themes.

Safer site access

• Blocking now runs through declarative network rules without per-site host permissions.
  The extension no longer requests "read and change your data" access to every blocked
  site on Firefox, so the install prompt shows far fewer permissions.
• Set a sensible minimum Firefox version (133.0) that correctly supports the no-permission
  blocking flow.