docs(gateway): update README with battery field, security fixes and warnings

- Add battery level field in MQTT payload example
- Replace echo with nano for secret file creation
- Add warning about bash history when writing passwords
- Add warning about hardcoded paths in gateway.service
- Update repository URL to new name
- Update validation checklist

gateway/README.md

@@ -12,7 +12,7 @@ remote MQTT broker on each reception.
 ```
 
 The gateway listens passively to BLE advertising packets and filters on the
-Nordic Configuration service UUID (`ef680100`). Each received packet is
+manufacturer data company_id `0xffff` as defined in the firmware specification. Each received packet is
 decoded following the firmware key/value specification and published
 immediately to the MQTT broker.
 
@@ -29,7 +29,8 @@ Example: `gateway_lausanne_01/C4:64:02:60:D9:16/update`
   "temp": 25.37,
   "humidity": 44,
   "co2_ppm": 400,
-  "window_open": false
+  "window_open": false,
+  "battery": 85	
 }
 ```
 
@@ -78,13 +79,21 @@ cp config.example.json config.json
 
 ## Usage
 
-Set the MQTT password as an environment variable before running:
+Set the MQTT password before running:
 
 ```bash
 mkdir -p ~/secrets
-echo "MQTT_PASSWORD=your_password" > ~/secrets/mqtt.env
+nano ~/secrets/mqtt.env
 chmod 600 ~/secrets/mqtt.env
-export MQTT_PASSWORD="your_password"
+```
+
+Add the following content to the file:
+MQTT_PASSWORD=your_password
+
+Warning: do not use echo to write the password — it will remain
+in your bash history. Always use a text editor like nano.
+
+```bash
 source venv/bin/activate
 python gateway.py
 ```
@@ -139,8 +148,8 @@ sudo apt install -y mosquitto mosquitto-clients
 
 **5. Clone the repository**
 ```bash
-git clone https://github.com/PI-E2EEDA/Plein-de-eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-project.git
-cd Plein-de-eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-project/gateway
+git clone https://github.com/PI-E2EEDA/Plein-de-eeeeeeeeee-project.git
+cd Plein-de-eeeeeeeeee-project/gateway
 ```
 
 **6. Create Python environment**
@@ -161,11 +170,17 @@ nano config.json
 **8. Create the secret file**
 ```bash
 mkdir -p ~/secrets
-echo "MQTT_PASSWORD=your_password" > ~/secrets/mqtt.env
+nano ~/secrets/mqtt.env
 chmod 600 ~/secrets/mqtt.env
 ```
+Add the following content to the file:
+MQTT_PASSWORD=your_password
 
 **9. Install the systemd service**
+Warning: the paths in gateway.service are hardcoded for the default
+pi user on Raspberry Pi OS. If you use a different username, update
+User, WorkingDirectory and ExecStart before copying the file.
+
 ```bash
 sudo cp gateway.service /etc/systemd/system/
 sudo systemctl daemon-reload
@@ -192,7 +207,8 @@ sudo systemctl status gateway
 ### Validation checklist
 - [ ] `active (running)` in systemctl status
 - [ ] Correct gateway ID in logs
-- [ ] MQTT connection established (`MQTT client connected`)
+- [ ] MQTT connection established (`Successfully connected to MQTT broker`)
+- [ ] Battery level included in published payload
 - [ ] TLS enabled (`TLS enabled`)
 - [ ] BLE scan started (`BLE scan started`)
 - [ ] Thingy:52 nodes detected in logs after power on