feat(shell): real sprout logo on home + basic Settings screen

- Bundle the real sprout logo (docs/logo.png → assets/logo.png) and show it on
  the home menu instead of a Material icon.
- Settings screen: switch language (Español / English / system) via slang, plus
  an About tile (logo, app name, one-line description). Drawer "Settings" is now
  active and routes to /settings.

Tests: drawer Settings opens the screen and shows the language options. 54 green.

apps/app_seeds/lib/i18n/es.i18n.json

@@ -23,6 +23,14 @@
     "following": "Siguiendo",
     "settings": "Ajustes"
   },
+  "settings": {
+    "language": "Idioma",
+    "systemLanguage": "Idioma del sistema",
+    "langEs": "Español",
+    "langEn": "English",
+    "about": "Acerca de",
+    "aboutText": "Inventario local y cifrado para semillas tradicionales. AGPL-3.0."
+  },
   "inventory": {
     "title": "Inventario",
     "searchHint": "Buscar semillas",