feat: complete migration to config flow and bugfixes (@38decibel)

* feat: migrate to config flow with device registry and brand icons

- Migrate all platforms to async_setup_entry (config flow)
- Each device now appears as a real HA device in the device registry
- Add device_info to all entities (cover, switch, button, sensor, binary_sensor)
- Add config_flow.py with airsend.yaml + !secret resolution
- Add strings.json for UI labels
- Fix unique_id bug (was splitting each character of the name)
- Split binary_sensor.py from sensor.py
- Bump version to 4.0

* Add icon for local brand

* Revise installation steps for AirSend integration

* Correction du crash websocket

raise Exception remplacé par return False

* Update README with AirSend configuration steps

Added instructions for configuring AirSend in Home Assistant.

* Update README with clearer instructions for YAML

Clarified instructions for editing the airsend.yaml file.

* Add files via upload

* Add English translation for AirSend configuration

* Add fr translations

* Update screenshot following latest version

* Fixe unavailable and new type light

Corrections de bugs
500 avec wait: true non fatal

Nouveau type
light.py — lumière dimmable (type 4100)

custom_components/airsend/translations/en.json

@@ -0,0 +1,31 @@
+{
+  "config": {
+    "step": {
+      "user": {
+        "title": "Set up AirSend",
+        "description": "The `airsend.yaml` file must be present in `/config`.\nThe internal URL is auto-detected if the AirSend addon is running.",
+        "data": {
+          "internal_url": "Internal URL (e.g. http://172.30.33.4:33863/)"
+        }
+      },
+      "reconfigure": {
+        "title": "Reconfigure AirSend",
+        "description": "Reload configuration from `airsend.yaml` and update the URL if needed.",
+        "data": {
+          "internal_url": "Internal URL"
+        }
+      }
+    },
+    "error": {
+      "no_devices": "No devices found in airsend.yaml. Check the `devices:` section.",
+      "yaml_not_found": "File airsend.yaml not found in /config. Please create it first.",
+      "cannot_connect": "Unable to reach the AirSend addon. Check that the addon is running and the URL is correct.",
+      "timeout": "The AirSend addon is not responding (timeout). Check that the addon is running.",
+      "no_url": "Please enter the internal URL of the AirSend addon."
+    },
+    "abort": {
+      "already_configured": "AirSend is already configured.",
+      "reconfigure_successful": "Reconfiguration successful."
+    }
+  }
+}