feat(browser): add POST /open with session restore and reader mode

- restores cookies and localStorage from DB before page navigation
- readerMode flag extracts plain text via @mozilla/readability (Firefox reader engine)
- add localStorage default '{}' on session entity for clean schema migrations

.gitignore

@@ -1,5 +1,6 @@
 /keys
 /node_modules
 /dist
+/data
 .env
 /*.log