feat: cliente Android offline-first (Kotlin + Jetpack Compose)

- Room (notes/outbox/categories/meta): edição 100% local, fila FIFO de mutações
- SyncEngine bidirecional: push (create/update com base_hash/delete, rekey de id
  local→servidor) + pull (categorias, notas divergentes, exclusões remotas)
- Conflito 409: servidor vence a nota + texto local preservado em cópia
  "Título (conflito)" enfileirada como create — nada perdido, sem relógios
- WorkManager: periódico 1h (rede + backoff exponencial), runNow único REPLACE
  em gatilhos (pós-save, rede restabelecida, boot, config, botão manual)
- OkHttp com timeout/retry em IOException; kotlinx.serialization; DataStore
- UI Compose: tela Servidor (URL+token+teste), Lista com banner de status
  (Offline/Sincronizando/Sincronizado/Erro/401 + pendências + conflitos),
  Editor com autosave por ociosidade (10 s) e categorias multi-seleção
- Build validado: assembleDebug (AGP 8.7.3/Kotlin 2.0.21/SDK 35, JDK 21) —
  app-debug.apk 17,6 MB; gradle-wrapper.jar fora do commit (regenerável com
  `gradle wrapper`, documentado no README)

app/src/main/java/com/labexposed/notas/MainActivity.kt

@@ -0,0 +1,98 @@
+package com.labexposed.notas
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.rememberNavController
+import com.labexposed.notas.domain.SyncPhase
+import com.labexposed.notas.domain.SyncUiState
+import com.labexposed.notas.ui.EditorScreen
+import com.labexposed.notas.ui.NotesListScreen
+import com.labexposed.notas.ui.NotasViewModel
+import com.labexposed.notas.ui.SettingsScreen
+import com.labexposed.notas.ui.theme.NotasTheme
+
+class MainActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContent {
+            NotasTheme { NotasApp_() }
+        }
+    }
+}
+
+@Composable
+private fun NotasApp_(vm: NotasViewModel = viewModel()) {
+    val nav = rememberNavController()
+    val settings by vm.settings.collectAsState()
+
+    NavHost(navController = nav, startDestination = if (settings.configured) "list" else "settings") {
+        composable("settings") {
+            SettingsScreen(vm, onDone = { nav.navigate("list") { popUpTo("settings") { inclusive = true } } })
+        }
+        composable("list") {
+            NotesListScreen(
+                vm = vm,
+                onOpen = { nav.navigate("editor/$it") },
+                onNew = { nav.navigate("editor/" + vm.createLocal()) },
+                onSettings = { nav.navigate("settings") },
+            )
+        }
+        composable("editor/{id}") { entry ->
+            val id = entry.arguments?.getString("id") ?: return@composable
+            EditorScreen(vm = vm, noteId = id, onBack = { nav.popBackStack() })
+        }
+    }
+}
+
+/** Banner de status: Offline · Sincronizando · Sincronizado · Erro · pendências. */
+@Composable
+fun SyncBanner(state: SyncUiState, modifier: Modifier = Modifier) {
+    val (bg, fg, label) = when (state.phase) {
+        SyncPhase.NotConfigured -> Quinteto(Color(0xFF9A9A9A), Color.White, "Configure o servidor ⚙")
+        SyncPhase.Offline -> Quinteto(Color(0xFF6F6F6F), Color.White, "Offline — ${state.pendingCount} alteração(ões) na fila")
+        SyncPhase.Syncing -> Quinteto(Color(0xFF3584E4), Color.White, "Sincronizando…")
+        SyncPhase.Synced -> {
+            val pend = if (state.pendingCount > 0) " · ${state.pendingCount} pendente(s)" else ""
+            val conf = if (state.conflicts > 0) " · ⚠ ${state.conflicts} conflito(s)" else ""
+            val hora = java.text.DateFormat.getTimeInstance(java.text.DateFormat.SHORT)
+                .format(java.util.Date(state.lastSyncAt))
+            Quinteto(Color(0xFF2EC27E), Color(0xFF073042), "Sincronizado às $hora$pend$conf")
+        }
+        SyncPhase.Error -> Quinteto(Color(0xFFE01B24), Color.White, "Erro: ${state.message}")
+        SyncPhase.Unauthorized -> Quinteto(Color(0xFFE01B24), Color.White, "Token inválido — revise em Servidor")
+    }
+    Surface(color = bg, shape = RoundedCornerShape(bottomStart = 12.dp, bottomEnd = 12.dp)) {
+        Row(
+            modifier = modifier.fillMaxWidth().padding(horizontal = 16.dp, vertical = 8.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.SpaceBetween,
+        ) {
+            Text(label, color = fg, style = MaterialTheme.typography.labelLarge)
+            if (state.dirtyCount > 0 && state.phase == SyncPhase.Synced) {
+                Text("● ${state.dirtyCount} não enviado(s)", color = fg, style = MaterialTheme.typography.labelMedium)
+            }
+        }
+    }
+}
+
+private data class Quinteto(val bg: Color, val fg: Color, val label: String)