feat: add dark mode support

[phillip9933]

Summary

Adds dark mode support by replacing hardcoded white backgrounds with theme-aware DayNight attributes across the app.
Closes #23

Changes

• Updated the base app theme (styles.xml) to use platform semantic background attributes linked to theme_color_background.
• Updated FileListAdapter and item_file_list.xml to use ?attr/colorSurface instead of hardcoded white backgrounds.
• Migrated secondary layouts (pattern lock, passcode, empty states, navigation containers) to use
  ?android:attr/colorBackground.
• Fixed the top progress bar drawable to respect the theme surface color.

Testing

• Built and verified locally using ./gradlew :opencloudApp:assembleOriginalDebug.
• Tested light and dark mode toggling in the app settings on an emulator.

[Copilot]

🟡 Changes recommended

The new Appearance preference handling has a correctness issue for missing/invalid persisted values, and there are dark-mode theming gaps (e.g., selection and dialogs) that should be addressed before merging.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR introduces app-wide dark mode support by switching to a DayNight base theme and migrating many UI surfaces/text to theme-resolved semantic colors, plus adds a user-facing appearance mode setting.

Changes:

• Switch Theme.openCloud to Theme.AppCompat.DayNight.* and introduce semantic color tokens with values-night overrides.
• Replace hardcoded light colors in many layouts/drawables with ?attr/* / ?android:attr/* theme attributes.
• Add an “Appearance” setting backed by an AppearanceMode enum and apply it at app startup via AppCompatDelegate.

File summaries

File	Description
opencloudApp/src/test/java/eu/opencloud/android/presentation/settings/AppearanceModeTest.kt	Adds unit tests for preference-to-night-mode mapping.
opencloudApp/src/main/res/xml/settings.xml	Adds the Appearance ListPreference to settings screen.
opencloudApp/src/main/res/values/styles.xml	Switches base theme to DayNight; adds semantic theme color items.
opencloudApp/src/main/res/values/strings.xml	Adds Appearance preference strings.
opencloudApp/src/main/res/values/colors.xml	Adds DayNight semantic color tokens (light defaults).
opencloudApp/src/main/res/values-night/colors.xml	Adds DayNight semantic color tokens (dark overrides).
opencloudApp/src/main/res/layout/whats_new_element.xml	Updates text colors to theme-aware colorOnPrimary.
opencloudApp/src/main/res/layout/whats_new_activity.xml	Updates skip button text color to theme-aware colorOnPrimary.
opencloudApp/src/main/res/layout/uploader_list_item_layout.xml	Migrates uploader list text colors to colorOnSurface*.
opencloudApp/src/main/res/layout/uploader_layout.xml	Migrates list divider color to theme colorOutline.
opencloudApp/src/main/res/layout/upload_list_item.xml	Migrates upload list text colors to colorOnSurface*.
opencloudApp/src/main/res/layout/upload_bottom_sheet_fragment.xml	Migrates bottom sheet background/divider/title colors to theme.
opencloudApp/src/main/res/layout/ssl_validator_layout.xml	Migrates SSL validator text color to colorOnSurface.
opencloudApp/src/main/res/layout/ssl_untrusted_cert_layout.xml	Migrates SSL untrusted cert header color to colorOnSurface.
opencloudApp/src/main/res/layout/spaces_list_item.xml	Migrates card background and text colors to surface/on-surface.
opencloudApp/src/main/res/layout/space_path_line.xml	Migrates icon/text tint to colorOnSurfaceVariant.
opencloudApp/src/main/res/layout/space_header.xml	Migrates header backgrounds and text colors to surface/on-surface.
opencloudApp/src/main/res/layout/sort_options_layout.xml	Migrates bottom sheet header text/icon tint to colorOnPrimary.
opencloudApp/src/main/res/layout/sort_bottom_sheet_fragment.xml	Migrates bottom sheet background/divider/title colors to theme.
opencloudApp/src/main/res/layout/share_user_item.xml	Migrates share user item text color to colorOnSurface.
opencloudApp/src/main/res/layout/share_public_link_item.xml	Migrates public link item title color to colorOnSurface.
opencloudApp/src/main/res/layout/share_public_dialog.xml	Migrates dialog label/secondary text colors to theme-aware attrs.
opencloudApp/src/main/res/layout/share_file_layout.xml	Migrates share file sheet colors to on-surface/on-primary.
opencloudApp/src/main/res/layout/remove_files_dialog.xml	Migrates dialog card/text colors to surface/on-surface.
opencloudApp/src/main/res/layout/rate_me_dialog.xml	Migrates button text to colorOnPrimary.
opencloudApp/src/main/res/layout/passcodelock.xml	Migrates passcode lock backgrounds/text to theme attributes.
opencloudApp/src/main/res/layout/opencloud_toolbar.xml	Migrates toolbar text/drawable tint to colorOnPrimary.
opencloudApp/src/main/res/layout/newfile_bottom_sheet_fragment.xml	Migrates bottom sheet background/divider/title colors to theme.
opencloudApp/src/main/res/layout/nav_main_container.xml	Migrates main container background to platform background attr.
opencloudApp/src/main/res/layout/nav_drawer_header.xml	Migrates drawer header text color to colorOnPrimary.
opencloudApp/src/main/res/layout/nav_drawer_footer.xml	Migrates drawer footer text colors to on-surface variants.
opencloudApp/src/main/res/layout/nav_drawer_content.xml	Sets drawer backgrounds to theme colorSurface.
opencloudApp/src/main/res/layout/nav_coordinator_layout.xml	Migrates bottom nav icon/text tint to colorOnPrimary.
opencloudApp/src/main/res/layout/manage_accounts_dialog.xml	Migrates dialog card/text/icon tint to theme attributes.
opencloudApp/src/main/res/layout/main_file_list_fragment.xml	Migrates FAB label/icon colors to colorOnPrimary.
opencloudApp/src/main/res/layout/log_list_item.xml	Migrates log list text colors to on-surface variants.
opencloudApp/src/main/res/layout/list_footer.xml	Migrates footer text color to colorOnSurfaceVariant.
opencloudApp/src/main/res/layout/item_file_list.xml	Adds surface background + migrates text/tints to on-surface variants.
opencloudApp/src/main/res/layout/item_empty_dataset.xml	Migrates empty state tint/text colors to theme attributes.
opencloudApp/src/main/res/layout/grid_item.xml	Migrates grid item text color to colorOnSurface.
opencloudApp/src/main/res/layout/fragment_migration_progress.xml	Migrates wizard background/text/progress tint to primary/on-primary.
opencloudApp/src/main/res/layout/fragment_migration_intro.xml	Migrates wizard background/text/button tint to primary/on-primary.
opencloudApp/src/main/res/layout/fragment_migration_completed.xml	Migrates wizard background/text/button tint to primary/on-primary.
opencloudApp/src/main/res/layout/fragment_migration_choice.xml	Migrates wizard background/text/button tint to primary/on-primary.
opencloudApp/src/main/res/layout/file_options_bottom_sheet_fragment.xml	Migrates bottom sheet background/text/divider to theme attrs.
opencloudApp/src/main/res/layout/file_details_fragment.xml	Migrates card/background/dividers to surface/outline theme attrs.
opencloudApp/src/main/res/layout/file_details_empty.xml	Migrates empty background to platform background attr.
opencloudApp/src/main/res/layout/edit_share_layout.xml	Migrates secondary text color to colorOnSurfaceVariant.
opencloudApp/src/main/res/layout/dialog_file_already_exists.xml	Migrates dialog card/text colors to surface/on-surface.
opencloudApp/src/main/res/layout/create_shortcut_dialog.xml	Migrates labels/disabled button text to on-surface variants.
opencloudApp/src/main/res/layout/activity_pattern_lock.xml	Migrates background/text colors to theme attributes.
opencloudApp/src/main/res/layout/account_item.xml	Migrates account item text/icon tints to on-surface variants.
opencloudApp/src/main/res/layout/account_action.xml	Migrates account action icon/text to on-surface colors.
opencloudApp/src/main/res/drawable/top_progress_bar_determinate.xml	Makes progress bar background use theme colorSurface.
opencloudApp/src/main/java/eu/opencloud/android/presentation/settings/SettingsFragment.kt	Wires up Appearance preference and applies night mode on change.
opencloudApp/src/main/java/eu/opencloud/android/presentation/settings/AppearanceMode.kt	Introduces AppearanceMode enum + preference mapping helper.
opencloudApp/src/main/java/eu/opencloud/android/presentation/files/filelist/FileListAdapter.kt	Replaces hardcoded white with theme colorSurface for file list items.
opencloudApp/src/main/java/eu/opencloud/android/MainApp.kt	Applies persisted appearance mode at application startup.
opencloudApp/src/androidTest/java/eu/opencloud/android/settings/SettingsFragmentTest.kt	Extends UI test to validate Appearance preference configuration.

Review details

• Files reviewed: 59/59 changed files
• Comments generated: 3
• Review effort level: Lite

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[phillip9933]

thanks for the sanity check with co-pilot. I've updated the issues it called out, should be ready for re-review