Release v0.1.2: site-backup persistence + PNG toolbar icons

- Mirror dismissals to window.localStorage on autotrader.co.uk ("atm:..."
  key). If browser.storage.local comes up empty after a quirky reinstall,
  the content script rehydrates from the site backup on the next page load.
- Replace the SVG toolbar icon with PNG renders (16/32/48/96/128) — some
  Firefox installs don't render extension SVG icons reliably in the
  toolbar / extensions flyout.
- Sharp added as a devDependency to rebuild icons from icon.svg.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dist/updates.json

@@ -9,6 +9,10 @@
         {
           "version": "0.1.1",
           "update_link": "https://git.nocker.cloud/tony/autotrader-marker/raw/branch/main/dist/autotrader-marker-0.1.1.xpi"
+        },
+        {
+          "version": "0.1.2",
+          "update_link": "https://git.nocker.cloud/tony/autotrader-marker/raw/branch/main/dist/autotrader-marker-0.1.2.xpi"
         }
       ]
     }