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/views/auth.py

@@ -0,0 +1,46 @@
+from fastapi import APIRouter, HTTPException, Request
+from fastapi.responses import RedirectResponse
+
+from app.core.auth import get_oauth
+from app.core.settings import get_settings
+
+router = APIRouter()
+
+
+@router.get("/login", include_in_schema=False)
+async def login(request: Request):
+    settings = get_settings()
+    if not settings.azure_configured:
+        raise HTTPException(
+            status_code=500,
+            detail=(
+                "Azure Entra ID auth is not configured. Set AZURE_TENANT_ID, "
+                "AZURE_CLIENT_ID, and AZURE_CLIENT_SECRET."
+            ),
+        )
+
+    oauth = get_oauth()
+    redirect_uri = request.url_for("auth_callback")
+    return await oauth.azure.authorize_redirect(request, redirect_uri)
+
+
+@router.get("/auth/callback", include_in_schema=False, name="auth_callback")
+async def auth_callback(request: Request):
+    oauth = get_oauth()
+    token = await oauth.azure.authorize_access_token(request)
+    userinfo = token.get("userinfo")
+    if not userinfo:
+        userinfo = await oauth.azure.parse_id_token(request, token)
+
+    request.session["user"] = {
+        "sub": userinfo.get("sub"),
+        "name": userinfo.get("name") or userinfo.get("preferred_username"),
+        "email": userinfo.get("email") or userinfo.get("preferred_username"),
+    }
+    return RedirectResponse(url="/", status_code=302)
+
+
+@router.get("/logout", include_in_schema=False)
+async def logout(request: Request):
+    request.session.clear()
+    return RedirectResponse(url="/", status_code=302)