fix(main): 대화 탭 로그인 가드를 적용한다

app/src/test/java/kr/co/vividnext/sodalive/v2/main/MainV2ActivitySourceTest.kt

@@ -46,6 +46,48 @@ class MainV2ActivitySourceTest {
         assertTrue(dmRouteIndex < firstFallbackIndex)
     }
 
+    @Test
+    fun `MainV2Activity 대화 탭 이동은 로그인 가드를 통과한 뒤 탭을 전환한다`() {
+        val source = projectFile("app/src/main/java/kr/co/vividnext/sodalive/v2/main/MainV2Activity.kt").readText()
+
+        assertTrue(source.contains("private fun selectChatTabWithLoginGuard(): Boolean"))
+
+        val guardSource = source.substringFrom("private fun selectChatTabWithLoginGuard(): Boolean")
+        assertBefore(guardSource, "if (!isLoggedIn())", "viewModel.clickTab(MainV2Tab.CHAT)")
+        assertBefore(guardSource, "showLoginActivity()", "return false")
+        assertTrue(guardSource.contains("return true"))
+
+        val setupViewSource = source.substringFrom("override fun setupView()")
+        assertTrue(setupViewSource.contains("selectChatTabWithLoginGuard()"))
+        assertFalse(setupViewSource.contains("viewModel.clickTab(MainV2Tab.CHAT)"))
+
+        val openChatTabSource = source.substringFrom("fun openChatTab()")
+        assertTrue(openChatTabSource.contains("selectChatTabWithLoginGuard()"))
+        assertFalse(openChatTabSource.contains("viewModel.clickTab(MainV2Tab.CHAT)"))
+
+        val openChatFilterSource = source.substringFrom("private fun openChatWithInitialFilter()")
+        assertTrue(openChatFilterSource.contains("selectChatTabWithLoginGuard()"))
+        assertFalse(openChatFilterSource.contains("viewModel.clickTab(MainV2Tab.CHAT)"))
+
+        val navigationSource = source.substringFrom("private fun setupBottomNavigation()")
+        assertTrue(navigationSource.contains("R.id.menu_main_v2_chat -> selectChatTabWithLoginGuard()"))
+    }
+
+    private fun assertBefore(source: String, expectedBefore: String, expectedAfter: String) {
+        val beforeIndex = source.indexOf(expectedBefore)
+        val afterIndex = source.indexOf(expectedAfter, beforeIndex)
+
+        assertTrue("Missing source: $expectedBefore", beforeIndex >= 0)
+        assertTrue("Missing source after $expectedBefore: $expectedAfter", afterIndex > beforeIndex)
+    }
+
+    private fun String.substringFrom(marker: String): String {
+        val startIndex = indexOf(marker)
+        assertTrue("Missing function: $marker", startIndex >= 0)
+        val nextFunctionIndex = indexOf("\n    private fun ", startIndex + marker.length).takeIf { it >= 0 } ?: length
+        return substring(startIndex, nextFunctionIndex)
+    }
+
     private fun projectFile(relativePath: String): File {
         val candidates = listOf(File(relativePath), File("../$relativePath"))
         return candidates.firstOrNull { it.exists() }