Feature Flags on chain

### Is your feature request related to a problem?

_No response_

### Describe the solution you'd like

Add a feature to manage Archethic apps feature flags directly on chain
Create a new service on AEApp keychain to manage the configuration

```
{
"applications": [
{
"applicationCode": "aeWallet",
"features": {
"ios": {
"featureA": true,
"featureB": false,
"featureC": true
},
"macos": {
"featureA": true,
"featureB": false,
"featureC": false
},
"web": {
"featureA": true,
"featureB": false,
"featureD": true
},
"android": {
"featureA": false,
"featureC": true,
"featureD": true
}
}
},
{
"applicationCode": "anotherApp",
"features": {
"ios": {
"featureA": false,
"featureB": true,
"featureC": false
},
"android": {
"featureA": true,
"featureC": false,
"featureD": true
}
}
}
]
}

```

### Additional context

_No response_

### Epic

_No response_

Start by locating the AEApp keychain entry point and reviewing how application configuration is currently managed. Define the on-chain feature-flag service around the issue's applicationCode and per-platform features schema, then verify that flags can be managed for the listed app and platform combinations.

Written by the indexing model from the issue text.