feat: Initial project structure for expense tracker

This commit introduces the initial project structure for the expense tracker application. It includes the basic directory layout, configuration files, a FastAPI server with a `/process-expense` endpoint for n8n integration, and a `.gitignore` file to ensure a clean repository. This completes Phase 1 of the development plan.

src/main.py

@@ -0,0 +1,21 @@
+from fastapi import FastAPI, Request
+import logging
+
+# Configure logging
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+app = FastAPI()
+
+@app.get("/")
+async def root():
+    return {"message": "Expense Tracker API is running."}
+
+@app.post("/process-expense")
+async def process_expense(request: Request):
+    """
+    Receives expense data from n8n, logs it, and returns a confirmation.
+    """
+    payload = await request.json()
+    logger.info(f"Received expense data: {payload}")
+    return {"status": "received", "data": payload}