feat: enhance avatar handling and file attachment functionality with improved UI interactions

app/src/main/java/com/rosetta/messenger/network/Protocol.kt

@@ -313,17 +313,29 @@ class Protocol(
         log("   Public key: ${publicKey.take(20)}...")
         log("   Private hash: ${privateHash.take(20)}...")
         log("   Current state: ${_state.value}")
-        
+
+        // Detect account switch: already authenticated but with different credentials
+        val switchingAccount = (_state.value == ProtocolState.AUTHENTICATED || _state.value == ProtocolState.HANDSHAKING) &&
+                               lastPublicKey != null && lastPublicKey != publicKey
+
         // Save credentials for reconnection
         lastPublicKey = publicKey
         lastPrivateHash = privateHash
-        
+
+        // If switching accounts, force disconnect and reconnect with new credentials
+        if (switchingAccount) {
+            log("🔄 Account switch detected, forcing reconnect with new credentials")
+            disconnect()
+            connect() // Will auto-handshake with saved credentials (publicKey, privateHash) on connect
+            return
+        }
+
         // КРИТИЧНО: если уже в handshake или authenticated, не начинаем заново
         if (_state.value == ProtocolState.HANDSHAKING) {
             log("⚠️ HANDSHAKE IGNORED: Already handshaking")
             return
         }
-        
+
         if (_state.value == ProtocolState.AUTHENTICATED) {
             log("⚠️ HANDSHAKE IGNORED: Already authenticated")
             return

app/src/main/java/com/rosetta/messenger/network/ProtocolManager.kt

@@ -35,6 +35,10 @@ object ProtocolManager {
     // Typing status
     private val _typingUsers = MutableStateFlow<Set<String>>(emptySet())
     val typingUsers: StateFlow<Set<String>> = _typingUsers.asStateFlow()
+
+    // Сигнал обновления own profile (username/name загружены с сервера)
+    private val _ownProfileUpdated = MutableStateFlow(0L)
+    val ownProfileUpdated: StateFlow<Long> = _ownProfileUpdated.asStateFlow()
     
     // 🔍 Global user info cache (like Desktop's InformationProvider.cachedUsers)
     // publicKey → SearchUser (resolved via PacketSearch 0x03)
@@ -200,6 +204,7 @@ object ProtocolManager {
                             if (user.username.isNotBlank()) {
                                 accountManager.updateAccountUsername(user.publicKey, user.username)
                             }
+                            _ownProfileUpdated.value = System.currentTimeMillis()
                         }
                     }
                 }