P2 Stream F + Stream U fix: JoinResidenceScreen + Coil test compile fix

Stream F: Convert JoinResidenceDialog -> dedicated screen matching iOS
JoinResidenceView. Invite-code input + inline validation + API success
navigates to residence detail.

Stream U fix: coil3 3.0.4 doesn't ship ColorImage (added in 3.1.0). Use
a minimal FakeImage test-double so CoilAuthInterceptorTest compiles.

Also completes consolidation of wave-3 work: all 6 parallel streams
(D/E/F/H/O/S/U) now landed. Full unit suite green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/com/tt/honeyDue/App.kt

@@ -486,6 +486,9 @@ fun App(
                     onAddResidence = {
                         navController.navigate(AddResidenceRoute)
                     },
+                    onJoinResidence = {
+                        navController.navigate(JoinResidenceRoute)
+                    },
                     onNavigateToProfile = {
                         navController.navigate(ProfileRoute)
                     },
@@ -502,6 +505,16 @@ fun App(
                 )
             }
 
+            composable<JoinResidenceRoute> {
+                com.tt.honeyDue.ui.screens.residence.JoinResidenceScreen(
+                    onNavigateBack = { navController.popBackStack() },
+                    onJoined = { residenceId ->
+                        navController.popBackStack()
+                        navController.navigate(ResidenceDetailRoute(residenceId))
+                    },
+                )
+            }
+
             composable<AddResidenceRoute> {
                 AddResidenceScreen(
                     onNavigateBack = {