feat: optimize network stack (#404)

* feat: optimize network stack and connection management

Refactor OkHttp connection pools, consolidate Gson serialization, add network-aware WebSocket reconnects, and deduplicate concurrent requests.

* test: update mapping assertions for AuthExpired

* refactor: address PR review feedback on network stack

Simplify health check, improve authenticator cookie matching robustness, resolve nit imports, and add unit tests.

app/src/main/java/com/m57/hermescontrol/data/local/AuthManager.kt

@@ -63,7 +63,7 @@ object AuthManager {
     private val _tokenFlow = MutableStateFlow<String?>(null)
     val tokenFlow: StateFlow<String?> = _tokenFlow.asStateFlow()
 
-    private val gson = com.google.gson.Gson()
+    private val gson = com.m57.hermescontrol.data.remote.OkHttpProvider.gson
 
     /**
      * Initialise the encrypted preferences.