Add preferences for AirPods Identity and Encryption Keys

This commit introduces settings for users to input their AirPods' Identity Resolving Key (IRK) and Encryption Key. These keys, obtainable via a MacBook, allow CAPod to reliably identify the AirPods and decrypt detailed status information.

Key changes:
- Added new preferences in General Settings for IRK and Encryption Key.
- Implemented a custom dialog for key input, including validation and a link to a guide.
- Added a Moshi adapter for serializing/deserializing `ByteArray` to/from Base64 for storing the keys.
- Included new string resources for labels, descriptions, and explanations related to the keys.
- Added new icons for the key preferences.

app/src/main/res/drawable/ic_key_24.xml

@@ -0,0 +1,11 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal"
+    android:autoMirrored="true">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M7 14C5.9 14 5 13.1 5 12S5.9 10 7 10 9 10.9 9 12 8.1 14 7 14M12.6 10C11.8 7.7 9.6 6 7 6C3.7 6 1 8.7 1 12S3.7 18 7 18C9.6 18 11.8 16.3 12.6 14H16V18H20V14H23V10H12.6Z" />
+</vector>

app/src/main/res/drawable/ic_key_outline_24.xml

@@ -0,0 +1,11 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal"
+    android:autoMirrored="true">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M21 18H15V15H13.3C12.2 17.4 9.7 19 7 19C3.1 19 0 15.9 0 12S3.1 5 7 5C9.7 5 12.2 6.6 13.3 9H24V15H21V18M17 16H19V13H22V11H11.9L11.7 10.3C11 8.3 9.1 7 7 7C4.2 7 2 9.2 2 12S4.2 17 7 17C9.1 17 11 15.7 11.7 13.7L11.9 13H17V16M7 15C5.3 15 4 13.7 4 12S5.3 9 7 9 10 10.3 10 12 8.7 15 7 15M7 11C6.4 11 6 11.4 6 12S6.4 13 7 13 8 12.6 8 12 7.6 11 7 11Z" />
+</vector>

app/src/main/res/values/strings.xml

@@ -7,6 +7,11 @@
     <string name="general_upgrade_action">Upgrade</string>
     <string name="general_check_action">Check</string>
     <string name="general_close_action">Close</string>
+    <string name="general_save_action">Save</string>
+    <string name="general_guide_action">Guide</string>
+    <string name="general_continue_action">Continue</string>
+
+    <string name="general_example_label">E.g.: %s</string>
 
     <string name="upgrade_capod_label">Upgrade CAPod</string>
     <string name="upgrade_capod_description">Get additional features and support the developer.</string>
@@ -49,6 +54,13 @@
     <string name="settings_maindevice_address_none">None</string>
     <string name="settings_maindevice_model_label">Your device model</string>
     <string name="settings_maindevice_model_description">The model of your main device. This helps the app recognize your device when it is not connected to your phone.</string>
+    <string name="settings_maindevice_identitykey_label">Identity Key</string>
+    <string name="settings_maindevice_identitykey_description">Your device\'s Identity Resolving Key (IRK), which helps CAPod identify it among nearby devices.</string>
+    <string name="settings_maindevice_identitykey_explanation">AirPods frequently change their Bluetooth address for privacy. The IRK helps CAPod recognize your device. You need one-time access to a MacBook.</string>
+    <string name="settings_maindevice_encryptionkey_label">Encryption Key</string>
+    <string name="settings_maindevice_encryptionkey_description">Your device\'s encryption key, which allows CAPod to retrieve detailed status information.</string>
+    <string name="settings_maindevice_encryptionkey_explanation">AirPods send a status message, part of which is encrypted. The encryption key allows CAPod to decrypt the full message. You need one-time access to a MacBook.</string>
+
     <string name="settings_onepod_mode_label">One pod mode</string>
     <string name="settings_onepod_mode_description">Wearing both pods is not required, wearing a single pod is sufficient to trigger reactions.</string>
     <string name="settings_popup_caseopen_label">Show case popup</string>
@@ -134,6 +146,4 @@
     <string name="onboarding_body3">CAPod has no ads and does not collect your data.</string>
     <string name="onboarding_body4">You can upgrade to CAPod Pro to gain extra features and support development.</string>
 
-    <string name="general_continue_action">Continue</string>
-
 </resources>

app/src/main/res/xml/preferences_general.xml

@@ -41,6 +41,18 @@
             android:key="core.maindevice.model"
             android:summary="@string/settings_maindevice_model_description"
             android:title="@string/settings_maindevice_model_label" />
+
+        <Preference
+            android:icon="@drawable/ic_key_outline_24"
+            android:key="core.maindevice.identitykey"
+            android:summary="@string/settings_maindevice_identitykey_description"
+            android:title="@string/settings_maindevice_identitykey_label" />
+
+        <Preference
+            android:icon="@drawable/ic_key_24"
+            android:key="core.maindevice.encryptionkey"
+            android:summary="@string/settings_maindevice_encryptionkey_description"
+            android:title="@string/settings_maindevice_encryptionkey_label" />
     </PreferenceCategory>
 
     <PreferenceCategory