Initial commit: AutoTrader Marker Firefox extension

Mark AutoTrader listings as 'not wanted' on both search results and detail
pages. Includes the unlisted signing / auto-update pipeline (web-ext +
dist/updates.json polled by Firefox).

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

.gitignore

@@ -0,0 +1,6 @@
+node_modules/
+.web-ext-artifacts/
+*.log
+.DS_Store
+.env
+.env.local