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>

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "AutoTrader Marker",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "description": "Mark AutoTrader listings as 'not wanted' so you can spot the ones you haven't reviewed yet.",
   "permissions": [
     "storage"
@@ -27,12 +27,16 @@
   "action": {
     "default_title": "AutoTrader Marker",
     "default_popup": "popup.html",
-    "default_icon": "icon.svg"
+    "default_icon": {
+      "16": "icons/icon-16.png",
+      "32": "icons/icon-32.png",
+      "48": "icons/icon-48.png"
+    }
   },
   "icons": {
-    "48": "icon.svg",
-    "96": "icon.svg",
-    "128": "icon.svg"
+    "48": "icons/icon-48.png",
+    "96": "icons/icon-96.png",
+    "128": "icons/icon-128.png"
   },
   "browser_specific_settings": {
     "gecko": {