Add session timeout, refactor session manager, reduce code duplication, update icons & styling

crypto_vault_extension/manifest.json

@@ -9,17 +9,23 @@
     "activeTab"
   ],
 
+  "icons": {
+    "16": "icons/icon16.png",
+    "32": "icons/icon32.png",
+    "48": "icons/icon48.png",
+    "128": "icons/icon128.png"
+  },
+
   "background": {
     "service_worker": "background.js",
     "type": "module"
   },
 
-
-
   "action": {
     "default_popup": "popup.html",
     "default_icon": {
       "16": "icons/icon16.png",
+      "32": "icons/icon32.png",
       "48": "icons/icon48.png",
       "128": "icons/icon128.png"
     }