feat: add AppLayout, BrandLogo, ProfileMenu, and RouteBadge components

- Implemented AppLayout component for application shell with navigation and sidebar.
- Created BrandLogo component to display the application logo.
- Developed ProfileMenu component for user profile management with dropdown functionality.
- Added RouteBadge component to visually represent route numbers with color coding.

style: add CSS styles for Dashboard and Routes pages

- Introduced Dashboard.css for styling the dashboard layout and components.
- Created RoutesPage.css for styling the routes page, including filters and table layout.
- Added SchedulesPage.css for styling the schedules layout and route options.

.env.example

@@ -17,9 +17,11 @@ FCM_ENABLED=false
 FCM_TOPIC=route_alerts
 FCM_ANDROID_CHANNEL_ID=route_alerts
 FIREBASE_PROJECT_ID=
-# Standard Application Default Credentials path. Store the JSON file outside
-# the repository and leave this empty while FCM_ENABLED=false.
-GOOGLE_APPLICATION_CREDENTIALS=
+# Directory on the Docker host (VM/LXC inside Proxmox), mounted read-only.
+FIREBASE_SECRETS_DIR=/opt/polotsk-transit/secrets
+# Path inside the backend container. For a direct Node.js launch, replace it
+# with the absolute host path to the JSON file.
+GOOGLE_APPLICATION_CREDENTIALS=/run/secrets/firebase-service-account.json
 
 # Bootstrap admin
 BOOTSTRAP_ADMIN=true