IME Send action on the chat composer — enter sends

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/kotlin/io/flamenet/messenger/app/ChatScreens.kt

@@ -1429,6 +1429,19 @@ fun ColumnScope.ChatScreen(
                     color = MaterialTheme.colorScheme.onSurface,
                 ),
                 cursorBrush = SolidColor(MaterialTheme.colorScheme.primary),
+                // Return sends — same convention iOS now defaults to. The
+                // send button stays for anyone who taps instead.
+                singleLine = true,
+                keyboardOptions = androidx.compose.foundation.text.KeyboardOptions(
+                    imeAction = androidx.compose.ui.text.input.ImeAction.Send),
+                keyboardActions = androidx.compose.foundation.text.KeyboardActions(
+                    onSend = {
+                        if (draft.isNotBlank()) {
+                            model.sendMessage(draft)
+                            draft = ""
+                        }
+                    }
+                ),
                 modifier = Modifier.fillMaxWidth().testTag("draft"),
             )
         }