Deliver localized auth app with verification and go_router

Integrate themed login/signup, EN/RU localization, shared dummy providers, verification recovery screens and named URL routes. Store frontend guidelines, workflow skills, validation and delivery documentation. Related to #2, #3, #5 and #6.

frontend/app/web/manifest.json

@@ -0,0 +1,19 @@
+{
+  "name": "SXCHNGE",
+  "short_name": "SXCHNGE",
+  "start_url": ".",
+  "display": "standalone",
+  "background_color": "#f9faf6",
+  "theme_color": "#14221d",
+  "description": "SXCHNGE account preview.",
+  "orientation": "any",
+  "prefer_related_applications": false,
+  "icons": [
+    {
+      "src": "favicon.svg",
+      "sizes": "any",
+      "type": "image/svg+xml",
+      "purpose": "any"
+    }
+  ]
+}