feat: Material You colors, settings backup/restore, add LICENSE

- Material You toggle: bars/rings use wallpaper-derived system accents on
  Android 12+ (ThemeColors.sessionFill/weeklyFill), Claude brand colors otherwise
- Settings backup/restore via SAF (export/import JSON); session cookie never
  included so backups are safe to store anywhere
- Add source-available LICENSE (mirrors SyncFlow's), with Anthropic trademark note

Built + installed on emulator, launches clean.

app/src/main/java/me/khodak/claudeusage/MainActivity.kt

@@ -30,6 +30,33 @@ class MainActivity : AppCompatActivity() {
     private val notifPermLauncher =
         registerForActivityResult(ActivityResultContracts.RequestPermission()) { /* result handled silently */ }
 
+    /** SAF: pick a destination file and write the current settings JSON to it. */
+    private val exportLauncher =
+        registerForActivityResult(ActivityResultContracts.CreateDocument("application/json")) { uri ->
+            if (uri == null) return@registerForActivityResult
+            try {
+                contentResolver.openOutputStream(uri)?.use { it.write(prefs.exportSettings().toByteArray()) }
+                toast("Settings exported")
+            } catch (_: Exception) { toast("Export failed") }
+        }
+
+    /** SAF: pick a backup file and apply it. */
+    private val importLauncher =
+        registerForActivityResult(ActivityResultContracts.OpenDocument()) { uri ->
+            if (uri == null) return@registerForActivityResult
+            try {
+                val json = contentResolver.openInputStream(uri)?.bufferedReader()?.use { it.readText() } ?: ""
+                if (prefs.importSettings(json)) {
+                    toast("Settings restored")
+                    // Reflect restored prefs immediately: re-sync switches and redraw any widgets.
+                    binding.switchNotify.isChecked = prefs.isNotifyEnabled()
+                    binding.switchRingStyle.isChecked = prefs.getWidgetStyle() == PreferencesManager.STYLE_RINGS
+                    binding.switchMaterialYou.isChecked = prefs.isMaterialYou()
+                    ClaudeUsageWidget.notifyDataChanged(this)
+                } else toast("Not a valid settings file")
+            } catch (_: Exception) { toast("Import failed") }
+        }
+
     /** Live refresh loop that runs only while the app is in the foreground. */
     private var autoRefreshJob: Job? = null
 
@@ -67,6 +94,8 @@ class MainActivity : AppCompatActivity() {
 
         setupNotificationSettings()
         setupWidgetStyleSetting()
+        setupMaterialYouSetting()
+        setupBackupRestore()
 
         binding.btnDebug.setOnClickListener {
             if (binding.tvDebugInfo.visibility == android.view.View.GONE) {
@@ -122,6 +151,28 @@ class MainActivity : AppCompatActivity() {
         }
     }
 
+    /** Material You toggle — switches the bars/rings to wallpaper-derived accents (Android 12+). */
+    private fun setupMaterialYouSetting() {
+        binding.switchMaterialYou.isChecked = prefs.isMaterialYou()
+        binding.switchMaterialYou.setOnCheckedChangeListener { _, checked ->
+            prefs.setMaterialYou(checked)
+            ClaudeUsageWidget.notifyDataChanged(this)
+        }
+    }
+
+    /** Export/Import settings via the Storage Access Framework (no extra permissions needed). */
+    private fun setupBackupRestore() {
+        binding.btnExportSettings.setOnClickListener {
+            exportLauncher.launch("claude-usage-settings.json")
+        }
+        binding.btnImportSettings.setOnClickListener {
+            importLauncher.launch(arrayOf("application/json", "text/*", "*/*"))
+        }
+    }
+
+    private fun toast(msg: String) =
+        android.widget.Toast.makeText(this, msg, android.widget.Toast.LENGTH_SHORT).show()
+
     private fun requestNotificationPermission() {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU) return
         if (ContextCompat.checkSelfPermission(this, Manifest.permission.POST_NOTIFICATIONS)