fast api: clean setup doc

Docs/Services/FastAPI/01-Setup.md

@@ -1,12 +1,100 @@
+# FastAPI – Environment Setup
+
+This document describes the initial setup required to prepare a Python environment for developing a FastAPI application.
+The steps below ensure isolation, dependency management, and reproducibility across environments.
+
+---
+
+## Prerequisites
+
+Before starting, ensure the following are installed on your system:
+
+* Python 3.8 or higher
+* `pip` (Python package manager)
+* `venv` module (included by default with most Python installations)
+
+You can verify your Python version with:
+
+```bash
+python3 --version
+```
+
+---
+
+## Step 1: Create a Virtual Environment
+
+A virtual environment isolates project dependencies and prevents conflicts with system-wide Python packages.
+
+From the project root directory, run:
+
 ```bash
 python3 -m venv .venv
 ```
 
+This command creates a `.venv` directory containing the isolated Python environment.
+
+---
+
+## Step 2: Activate the Virtual Environment
+
+Activate the virtual environment before installing any dependencies.
+
+### Linux / macOS
+
+```bash
+source .venv/bin/activate
+```
+
+### Windows (PowerShell)
+
+```powershell
+.venv\Scripts\Activate.ps1
+```
+
+After activation, your shell prompt should indicate that the virtual environment is active.
+
+---
+
+## Step 3: Install FastAPI
+
+With the virtual environment activated, install FastAPI using `pip`:
 
 ```bash
 pip install fastapi
 ```
 
+This installs the FastAPI framework and its required dependencies.
+
+> Note: In a real application, FastAPI is commonly used with an ASGI server such as `uvicorn`, which can be installed later if needed.
+
+---
+
+## Step 4: Freeze Dependencies
+
+To ensure reproducibility across environments (local, CI/CD, staging, production), export the installed dependencies to a requirements file:
+
 ```bash
-pip freeze > requirment.txt
+pip freeze > requirement.txt
-```
+```
+
+This file should be committed to version control and used by deployment pipelines to install exact dependency versions.
+
+---
+
+## Resulting Files
+
+After completing the steps above, your project directory should include:
+
+* `.venv/` – Python virtual environment (should not be committed to VCS)
+* `requirement.txt` – Dependency lock file
+
+---
+
+## Best Practices
+
+* Always activate the virtual environment before working on the project
+* Do not commit `.venv/` to source control
+* Keep `requirement.txt` updated when adding or upgrading dependencies
+* Use the same `requirement.txt` in CI/CD pipelines for consistent builds
+
+---