refactor: improve router type safety and usage

- Add explicit Router type imports across views
- Replace $router type casting with proper typing
- Use $router.back() instead of $router.go(-1) for consistency
- Add proper route and router typings to components
- Clean up router navigation methods
- Fix router push/back method calls

This commit improves type safety and consistency in router usage across
the application's view components.

src/views/StartView.vue

@@ -102,6 +102,7 @@ import {
   components: {},
 })
 export default class StartView extends Vue {
+  $router!: Router;
   PASSKEYS_ENABLED = PASSKEYS_ENABLED;
 
   givenName = "";
@@ -115,22 +116,22 @@ export default class StartView extends Vue {
   }
 
   public onClickNewSeed() {
-    (this.$router as Router).push({ name: "new-identifier" });
+    this.$router.push({ name: "new-identifier" });
   }
 
   public async onClickNewPasskey() {
     const keyName =
       AppString.APP_NAME + (this.givenName ? " - " + this.givenName : "");
     await registerSaveAndActivatePasskey(keyName);
-    (this.$router as Router).push({ name: "account" });
+    this.$router.push({ name: "account" });
   }
 
   public onClickNo() {
-    (this.$router as Router).push({ name: "import-account" });
+    this.$router.push({ name: "import-account" });
   }
 
   public onClickDerive() {
-    (this.$router as Router).push({ name: "import-derive" });
+    this.$router.push({ name: "import-derive" });
   }
 }
 </script>