Add project documentation and initial analysis reports

docs/architecture-app.md

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+# Backend Architecture
+
+## Overview
+
+The PriceFlow backend is a high-performance API and worker service built with Python and FastAPI. It handles product management, scraping logic, database operations, and notifications.
+
+## Technology Stack
+
+- **Framework**: FastAPI (Python 3.12)
+- **Server**: Uvicorn (ASGI)
+- **Database**: PostgreSQL (via SQLAlchemy ORM)
+- **Migrations**: Alembic
+
+## Core Components
+
+### 1. API Layer (`app/routers`)
+
+Exposes REST endpoints for the frontend to consume. Handles request validation via Pydantic schemas.
+
+### 2. Service Layer (`app/services`)
+
+Contains the business logic, including:
+
+- **Scraping**: Logic to control Playwright/Browserless.
+- **AI Analysis**: Integration with LiteLLM for image processing.
+- **Notifications**: Apprise integration.
+
+### 3. Data Layer (`app/models.py`)
+
+Defines the database schema using SQLAlchemy.
+
+- **Models**: Products, Prices, Users (if applicable).
+
+### 4. Background Workers
+
+Uses `APScheduler` or similar mechanisms (implied from deps) to run periodic scraping tasks.
+
+## Scraping Architecture
+
+The backend delegates browser rendering to a separate `Browserless` service (Docker container) via WebSocket, ensuring the main API remains responsive.