feat: Initialize FastAPI application with Azure authentication and transaction management

- Added .env.example for environment variable configuration.
- Created app initialization files and core settings management.
- Implemented API routers for reporting and transaction endpoints.
- Developed transaction management service with CRUD operations.
- Integrated Azure OAuth for user authentication.
- Designed dashboard view with transaction filtering and display.
- Added Swagger UI documentation with custom dark theme.
- Created static and template files for frontend styling and layout.

.env.example

@@ -0,0 +1,4 @@
+SESSION_SECRET_KEY="replace-with-a-random-secret"
+AZURE_TENANT_ID="<your-tenant-id>"
+AZURE_CLIENT_ID="<your-client-id>"
+AZURE_CLIENT_SECRET="<your-client-secret>"