fix(firmware): auto-connect 시 Scan UI 조건부 숨김 (cloud-mvp d0e5ca7 이식)

target 설정된 상태 (auto-connect 성공) 에서는 Scan 버튼 · Devices 리스트 숨김.
target 없거나 IDLE/SCANNING phase 에서만 노출.

Fallback: 연결 없이 진입하거나 auto-connect 실패 시 기존 스캔 UI 유지.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/src/main/java/com/medithings/vesiscan/firmware/ui/FirmwareUpdateView.kt

@@ -233,9 +233,11 @@ fun DfuScreen(manager: DfuManager, modifier: Modifier = Modifier) {
         }
 
         // ── Actions ───────────────────────────────────────────────────────────────────────
+        // 2026-08-03: auto-connect 로 대부분 target 즉시 설정됨.
+        //   target 없는 경우 (fresh install · 새 기기) 에만 수동 Scan/Stop 노출.
+        val hasTarget = target != null
         Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
-            // Keyed off the phase, not the scanner: the DFU re-scan also runs the scanner, and
-            // stopping that one from here would abort the update.
+            if (!hasTarget || phase == DfuPhase.IDLE || phase == DfuPhase.SCANNING) {
                 if (phase == DfuPhase.SCANNING) {
                     OutlinedButton(onClick = { manager.stopScan() }) { Text("Stop") }
                 } else {
@@ -244,6 +246,7 @@ fun DfuScreen(manager: DfuManager, modifier: Modifier = Modifier) {
                         enabled = !manager.isBusy,
                     ) { Text("Scan") }
                 }
+            }
 
             Button(
                 onClick = { manager.startDfu() },
@@ -261,7 +264,8 @@ fun DfuScreen(manager: DfuManager, modifier: Modifier = Modifier) {
             }
         }
 
-        // ── Discovered devices ────────────────────────────────────────────────────────────
+        // ── Discovered devices — target 없을 때만 (auto-connect 실패 · 첫 사용) ────────
+        if (!hasTarget) {
             Text(
                 "Devices (${manager.devices.size})",
                 style = MaterialTheme.typography.labelLarge,
@@ -270,7 +274,6 @@ fun DfuScreen(manager: DfuManager, modifier: Modifier = Modifier) {
                 if (manager.devices.isEmpty()) {
                     Text(
                         when (phase) {
-                        DfuPhase.CONNECTED -> "Connected — disconnect to scan again."
                             DfuPhase.SCANNING -> "Scanning…"
                             else -> "No devices yet — tap Scan."
                         },
@@ -290,6 +293,7 @@ fun DfuScreen(manager: DfuManager, modifier: Modifier = Modifier) {
                     }
                 }
             }
+        }
 
         // ── Log ───────────────────────────────────────────────────────────────────────────
         Text("Log", style = MaterialTheme.typography.labelLarge)