Open app/main.py and replace its entire contents with:

from fastapi import FastAPI, Request, UploadFile, File, HTTPException
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates

from app.db import fetch_monthly_summary, fetch_retention_pen, fetch_campaigns

app = FastAPI()

app.mount("/static", StaticFiles(directory="app/static"), name="static")
templates = Jinja2Templates(directory="app/templates")


@app.get("/", response_class=HTMLResponse)
async def dashboard(request: Request):
    data = await fetch_monthly_summary()
    latest = data[-1] if data else None
    return templates.TemplateResponse(
        "dashboard.html",
        {"request": request, "latest": latest},
    )


@app.get("/api/monthly-summary")
async def api_monthly_summary():
    data = await fetch_monthly_summary()
    return {"data": data}


@app.get("/api/retention-pen")
async def api_retention_pen():
    data = await fetch_retention_pen()
    return {"data": data}


@app.get("/api/campaigns")
async def api_campaigns():
    data = await fetch_campaigns()
    return {"data": data}


# --- Data upload stub (CSV -> storage path placeholder) ---

from uuid import uuid4

async def upload_to_supabase_storage(file: UploadFile) -> str:
    """
    Stub implementation: in future this should upload to Supabase Storage.
    For now we just pretend and return a generated path.
    """
    return f"books/{uuid4()}-{file.filename}"


@app.post("/upload-book")
async def upload_book(file: UploadFile = File(...)):
    if not file.filename.endswith(".csv"):
        raise HTTPException(status_code=400, detail="Only CSV files are allowed")

    storage_path = await upload_to_supabase_storage(file)
    return {"message": "Upload complete", "path": storage_path}


# --- WhatsApp automation stub ---

from pydantic import BaseModel

class WhatsAppMessage(BaseModel):
    contact_id: str
    phone_number: str | None = None
    campaign_id: str | None = None
    message_preview: str

@app.post("/api/whatsapp/send")
async def send_whatsapp_stub(payload: WhatsAppMessage):
    # Later: push to Make/n8n or another service.
    print("WhatsApp stub queued:", payload.dict())
    return {
        "status": "queued",
        "detail": "WhatsApp message queued for external automation (stub).",
    }