feat(viewer): vendor the Viewer app in-tree

Import the rewritten Vue 3 Viewer app (nextcloud/viewer feat/6.0.0) into
apps/viewer as a bundled app and wire it into the shared frontend build:

- add the viewer entry + build/frontend/apps/viewer symlink to the shared vite
  config, and un-ignore apps/viewer
- add the viewer-only runtime deps (@nextcloud/image-editor, @skjnldsv/vue-plyr,
  dompurify, vue-material-design-icons, camelcase) to the root package.json
- vendor the plyr sprite as apps/viewer/img/plyr.svg and import it raw, instead
  of the standalone build.s PLYR_ICONS global / a blocked plyr deep import
- port the Vitest unit and component specs; run the viewer test setup
  (mock reset, handler registry reset, ResizeObserver stub) from the shared
  vitest config, and add the shared @nextcloud/event-bus manual mock
- cover the viewer l10n / img / composer files in REUSE.toml

WIP: Playwright e2e still to port.

Signed-off-by: skjnldsv <skjnldsv@protonmail.com>
Assisted-by: ClaudeCode:claude-opus-4-8

Author: skjnldsv

.gitignore

@@ -47,6 +47,7 @@ node_modules/
 !/apps/theming
 !/apps/twofactor_backupcodes
 !/apps/user_status
+!/apps/viewer
 !/apps/weather_status
 !/apps/webhook_listeners
 !/apps/workflowengine

.tx/config

@@ -205,3 +205,9 @@ file_filter = translationfiles/<lang>/workflowengine.po
 source_file = translationfiles/templates/workflowengine.pot
 source_lang = en
 type        = PO
+
+[o:nextcloud:p:nextcloud:r:viewer]
+file_filter = translationfiles/<lang>/viewer.po
+source_file = translationfiles/templates/viewer.pot
+source_lang = en
+type        = PO

REUSE.toml

@@ -344,3 +344,39 @@ path = ["openapi.json", ".envrc", "flake.nix", "flake.lock", "build/eslint-basel
 precedence = "aggregate"
 SPDX-FileCopyrightText = "2025 Nextcloud GmbH and Nextcloud contributors"
 SPDX-License-Identifier = "AGPL-3.0-or-later"
+
+[[annotations]]
+path = ["apps/viewer/l10n/**.js", "apps/viewer/l10n/**.json"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Nextcloud translators <https://www.transifex.com/nextcloud/>"
+SPDX-License-Identifier = "AGPL-3.0-or-later"
+
+[[annotations]]
+path = ["apps/viewer/img/blank.mp4"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2023 Nextcloud GmbH and Nextcloud contributors"
+SPDX-License-Identifier = "AGPL-3.0-or-later"
+
+[[annotations]]
+path = ["apps/viewer/img/app.svg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2018-2024 Google LLC"
+SPDX-License-Identifier = "Apache-2.0"
+
+[[annotations]]
+path = ["apps/viewer/img/plyr.svg"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "Sam Potts <sam@potts.es>"
+SPDX-License-Identifier = "MIT"
+
+[[annotations]]
+path = ["apps/viewer/composer.json", "apps/viewer/composer.lock"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2016-2024 Nextcloud GmbH and Nextcloud contributors"
+SPDX-License-Identifier = "CC0-1.0"
+
+[[annotations]]
+path = ["apps/viewer/src/assets/menu-sidebar-white.svg", "apps/viewer/tests/psalm-baseline.xml"]
+precedence = "aggregate"
+SPDX-FileCopyrightText = "2019 Nextcloud GmbH and Nextcloud contributors"
+SPDX-License-Identifier = "AGPL-3.0-or-later"

apps/viewer/.nextcloudignore

@@ -0,0 +1,4 @@
+# SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+/playwright

apps/viewer/.npmignore

@@ -0,0 +1,3 @@
+# SPDX-FileCopyrightText: 2019 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+node_modules

apps/viewer/.stylelintignore

@@ -0,0 +1,3 @@
+# SPDX-FileCopyrightText: 2022 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+src/assets

apps/viewer/AUTHORS.md

@@ -0,0 +1,65 @@
+<!--
+  - SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+  - SPDX-License-Identifier: AGPL-3.0-or-later
+-->
+# Authors
+
+- Adrian Thiele <adrian.thiele@live.de>
+- Andy Scherzinger <info@andy-scherzinger.de>
+- Anna Larch <anna@nextcloud.com>
+- Arne Hamann <git@arne.email>
+- Arthur Schiwon <blizzz@arthur-schiwon.de>
+- Axel Pirek <axel.pirek@protonmail.com>
+- Azul <azul@riseup.net>
+- Birk <birkb@users.noreply.github.com>
+- Carl Schwan <carl@carlschwan.eu>
+- Christoph Wurst <christoph@winzerhof-wurst.at>
+- Christopher Ng <chrng8@gmail.com>
+- Corentin Mors <corentin.mors@dashlane.com>
+- Daniel Calviño Sánchez <danxuliu@gmail.com>
+- Daniel Kesselberg <mail@danielkesselberg.de>
+- Dariusz Olszewski <starypatyk@users.noreply.github.com>
+- Eduardo Morales <emoral435@gmail.com>
+- fenn-cs <fenn25.fn@gmail.com>
+- Ferdinand Thiessen <opensource@fthiessen.de>
+- Florent Fayolle <florent.fayolle69@gmail.com>
+- Gary Kim <gary@garykim.dev>
+- Grigorii K. Shartsev <me@shgk.me>
+- Hamza Mahjoubi <hamzamahjoubi221@gmail.com>
+- Jakob Röhrl <jakob.roehrl@web.de>
+- Jakub Fiser <jakub@ufiseru.cz>
+- Jan-Christoph Borchardt <hey@jancborchardt.net>
+- jld3103 <jld3103yt@gmail.com>
+- Joas Schilling <coding@schilljs.com>
+- John Molakvoæ <skjnldsv@protonmail.com>
+- Jonas Meurer <jonas@freesources.org>
+- Julia Kirschenheuter <julia.kirschenheuter@nextcloud.com>
+- Julien Veyssier <eneiluj@posteo.net>
+- Julius Härtl <jus@bitgrid.net>
+- k9yyy <yyy3752@gmail.com>
+- Louis Chemineau <louis@chmn.me>
+- Luka Trovic <luka@nextcloud.com>
+- Marcel Müller <marcel-mueller@gmx.de>
+- Marco <marcoambrosini@pm.me>
+- Marius Blüm <marius@lineone.io>
+- Max <max@nextcloud.com>
+- Morris Jobke <hey@morrisjobke.de>
+- Pytal <24800714+Pytal@users.noreply.github.com>
+- rakekniven <2069590+rakekniven@users.noreply.github.com>
+- Raul <r.ferreira.fuentes@gmail.com>
+- Richard Steinmetz <richard@steinmetz.cloud>
+- Robbert Gurdeep Singh <git@beardhatcode.be>
+- Roeland Jago Douma <roeland@famdouma.nl>
+- root <szaimen@e.mail.de>
+- Sanskar Soni <sanskarsoni300@gmail.com>
+- Sebastian Steinmetz <462714+steiny2k@users.noreply.github.com>
+- Simon L. <szaimen@e.mail.de>
+- szaimen <szaimen@e.mail.de>
+- Talv <krz.krawczuk@gmail.com>
+- Tobias Speicher <rootcommander@gmail.com>
+- umgfoin <umgfoin@users.noreply.github.com>
+- Valdnet <47037905+Valdnet@users.noreply.github.com>
+- Vanessa Pertsch <vanessa.pertsch@posteo.de>
+- Varun Patil <varunpatil@ucla.edu>
+- Vincent Petry <vincent@nextcloud.com>
+- XinRoom <32238570+XinRoom@users.noreply.github.com>