feat: settings backup 29 (#160)

* docs: settings backup plan

* docs: car mode settings crash fix

* docs: backup format

* docs: perms

* feat: phase 1 and 2

* test: phase 1 and 2 test

* feat: UI

* feat: draw the rest of the fucking owl lol

* fix: narrow exceptions

* fix: bug bot

Car mode Bluetooth devices excluded from backup
High Severity

The EXCLUDED_KEYS set containing "A", "B", "C" is applied globally to
all preference files, but BTCarModeStorage uses key "A" for
carModeTriggerDevicesRaw (the user's configured Bluetooth devices).
Since exportSharedPreferences is called for both default and car mode
preferences with the same exclusion filter, the car mode Bluetooth
device configuration will never be exported. This defeats the purpose of
backing up car mode settings and results in data loss for users who rely
on this feature.

Long preferences become Int causing ClassCastException on import
High Severity

When importing settings to a fresh install, Long preferences that fit
within Int range (like versionCodeFirstInstalled) are incorrectly stored
as Int because prefs.all[key] returns null and the code defaults to
putInt. The app subsequently calls getLong() to read these values, which
throws a ClassCastException when the value is actually stored as Int.
This will crash the app after importing a backup to a new device or
fresh install.

* feat: calendar handled backup

* fix: and test best effort

* feat: better user feedback

* docs: review notes

* fix: build

* fix: bug bot

Car mode runtime state exported in backup
Medium Severity

The car mode preferences backup includes the carModeSilentUntil
timestamp (key "B") which is runtime state, not user configuration.
BTCarModeStorage uses "A" for trigger devices (user config) and "B" for
silent-until timestamp (runtime state). The code passes
excludeRuntimeState = false to avoid filtering out the "A" key, but this
also includes "B". When restored, a stale future timestamp could cause
car mode silent period to be incorrectly active on the new device,
affecting notification behavior until that time passes.

* fix: bug bot

Missing text reset causes wrong message after permission grant
Low Severity

When Bluetooth permission is denied, noDevicesText.text is set to the
"permission required" message. However, loadBluetoothDevices() only sets
the visibility, never resetting the text. If a user denies permission,
then grants it via app settings and returns, and has no paired Bluetooth
devices, they'll see "Bluetooth permission is required..." instead of
the correct "No known Bluetooth devices" message.

* test: fix

Author: williscool

android/app/src/main/AndroidManifest.xml

@@ -13,9 +13,14 @@
 
     <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
 
-    <uses-permission android:name="android.permission.BLUETOOTH" />
+    <!-- Legacy Bluetooth permission - only needed on API 30 and below -->
+    <uses-permission android:name="android.permission.BLUETOOTH" 
+        android:maxSdkVersion="30" />
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> <!-- this is also required for BlueTooth - according to google bluetooth device discovery can be used for coarse location -->
 
+    <!-- Android 12+ (API 31) - Required for accessing paired Bluetooth devices -->
+    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+    
     <!-- TODO: figure out how to only enable these for dev build -->
     <uses-permission android:name="android.permission.INTERNET" />
 

android/app/src/main/java/com/github/quarck/calnotify/backup/BackupData.kt

@@ -0,0 +1,60 @@
+//
+//   Calendar Notifications Plus
+//   Copyright (C) 2025 William Harris (wharris+cnplus@upscalews.com)
+//
+//   This program is free software; you can redistribute it and/or modify
+//   it under the terms of the GNU General Public License as published by
+//   the Free Software Foundation; either version 3 of the License, or
+//   (at your option) any later version.
+//
+//   This program is distributed in the hope that it will be useful,
+//   but WITHOUT ANY WARRANTY; without even the implied warranty of
+//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//   GNU General Public License for more details.
+//
+//   You should have received a copy of the GNU General Public License
+//   along with this program; if not, write to the Free Software Foundation,
+//   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
+//
+
+package com.github.quarck.calnotify.backup
+
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.JsonElement
+
+/**
+ * Per-calendar enabled/disabled setting with identifying info for cross-device matching.
+ * On import, calendars are matched by accountName+displayName.
+ */
+@Serializable
+data class CalendarSettingBackup(
+    val accountName: String,
+    val accountType: String,
+    val displayName: String,
+    val ownerAccount: String,
+    val name: String,
+    val enabled: Boolean
+)
+
+/**
+ * Root backup data structure.
+ * Version field allows future migrations if the schema changes.
+ */
+@Serializable
+data class BackupData(
+    val version: Int = CURRENT_VERSION,
+    val exportedAt: Long,
+    val appVersionCode: Long,
+    val appVersionName: String,
+    /** Main app settings from default SharedPreferences (excludes calendar_handled_ keys) */
+    val settings: Map<String, JsonElement>,
+    /** Car mode Bluetooth device settings */
+    val carModeSettings: Map<String, JsonElement>,
+    /** Per-calendar enabled settings with identifying info for cross-device matching */
+    val calendarSettings: List<CalendarSettingBackup> = emptyList()
+) {
+    companion object {
+        const val CURRENT_VERSION = 2
+    }
+}
+