Merge branch 'main' into feat-debug-reporting

Resolve conflicts from #40/#41/#44:
- build.gradle.kts: keep DEBUG_REPORT_ENDPOINT field + val, take #40's
  outlookRedirectScheme (gmailRedirectScheme was deleted).
- LibreMailApp.kt: function takes BOTH appViewModel (start-dest gating, #44)
  and startupViewModel (crash dialog, #42); use renamed AccountPickerScreen.
- SettingsScreen.kt: keep both the Diagnostics (#42) and Backup (#41) sections.
Verified locally: assembleDebug + testDebugUnitTest + lintDebug + ktlintCheck + detekt.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -30,8 +30,6 @@
     <string name="search_hint">Search mail</string>
     <string name="search_no_results">No results</string>
     <string name="mailbox_pull_to_refresh">Pull down to refresh</string>
-    <string name="mailbox_welcome_title">Welcome to LibreMail</string>
-    <string name="mailbox_welcome_subtitle">Add an account to start reading your mail.</string>
 
     <!-- Mailbox multi-select contextual action bar -->
     <string name="cab_selected_count">%1$d selected</string>
@@ -102,10 +100,36 @@
     <string name="attachment_download_failed">Couldn\'t download %1$s</string>
     <string name="attachment_no_app">No app can open this file</string>
 
-    <!-- Account setup -->
-    <string name="account_setup_outlook">Sign in with Microsoft</string>
+    <!-- Onboarding -->
+    <string name="onboarding_welcome_title">Welcome to LibreMail</string>
+    <string name="onboarding_welcome_subtitle">A private, open-source home for all your email. Add your first account to get started.</string>
+    <string name="onboarding_add_account">Add an email account</string>
+    <string name="onboarding_account_added_title">Account added</string>
+    <string name="onboarding_add_another_prompt">Would you like to add another email account?</string>
+    <string name="onboarding_add_another_yes">Add another account</string>
+    <string name="onboarding_add_another_no">No, take me to my inbox</string>
+
+    <!-- Account setup (vendor picker) -->
+    <string name="account_setup_outlook">Outlook or Hotmail</string>
     <string name="account_setup_other">Other (IMAP/SMTP)</string>
-    <string name="account_setup_subtitle">Choose how you want to connect your mailbox.</string>
+    <string name="account_setup_subtitle">Choose your email provider to get started.</string>
+
+    <!-- App-password guided setup (Gmail/Yahoo/iCloud) -->
+    <string name="app_password_title">Connect %1$s</string>
+    <string name="app_password_unknown_provider">Unknown email provider.</string>
+    <string name="app_password_intro_gmail">To connect Gmail, create an app password in your Google Account. Gmail requires 2-Step Verification to be turned on before you can create one.</string>
+    <string name="app_password_intro_yahoo">To connect Yahoo Mail, generate an app password from your Yahoo Account security settings.</string>
+    <string name="app_password_intro_icloud">To connect iCloud Mail, create an app-specific password from your Apple ID account page.</string>
+    <string name="app_password_what_is">An app password is a one-off password that lets an app sign in to your account without your main password or a two-factor code.</string>
+    <string name="app_password_warning">Store this app password carefully — it grants full access to your email. LibreMail keeps it only on this device.</string>
+    <string name="app_password_open_page">Create an app password for %1$s</string>
+    <string name="app_password_open_failed">Couldn\'t open your browser</string>
+    <string name="app_password_email">Email address</string>
+    <string name="app_password_field">App password</string>
+    <string name="app_password_show_servers">Server settings</string>
+    <string name="app_password_server_imap">Incoming (IMAP): %1$s:%2$d (%3$s)</string>
+    <string name="app_password_server_smtp">Outgoing (SMTP): %1$s:%2$d (%3$s)</string>
+    <string name="app_password_test_and_add">Test &amp; add account</string>
 
     <!-- Manual IMAP/SMTP setup -->
     <string name="manual_setup_title">IMAP / SMTP</string>
@@ -143,6 +167,11 @@
     <string name="settings_no_accounts">No accounts yet</string>
     <string name="account_remove">Remove account</string>
 
+    <!-- Backup -->
+    <string name="settings_backup">Backup</string>
+    <string name="settings_backup_include">Include settings in Android Backup</string>
+    <string name="settings_backup_include_summary">Let Android back up your LibreMail preferences (Google Auto Backup) so they restore when you set up a new device. Your mail, accounts, passwords, and encryption keys are never backed up — only app settings. Off by default; uses Google infrastructure.</string>
+
     <!-- Per-account settings -->
     <string name="settings_account_title">Account</string>
     <string name="settings_signature">Signature</string>