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.

app/core/auth.py

@@ -0,0 +1,22 @@
+from functools import lru_cache
+
+from authlib.integrations.starlette_client import OAuth
+
+from app.core.settings import get_settings
+
+
+@lru_cache
+def get_oauth() -> OAuth:
+    settings = get_settings()
+    oauth = OAuth()
+    oauth.register(
+        name="azure",
+        client_id=settings.azure_client_id,
+        client_secret=settings.azure_client_secret,
+        server_metadata_url=(
+            f"https://login.microsoftonline.com/{settings.azure_tenant_id}"
+            "/v2.0/.well-known/openid-configuration"
+        ),
+        client_kwargs={"scope": "openid profile email"},
+    )
+    return oauth