feat: add photo roll to preview app

[AlexAndBear]

Description

Related Issue

• Fixes <issue_link>

How Has This Been Tested?

• test environment:
• test case 1:
• test case 2:
• ...

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification that affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)

[Copilot]

Pull request overview

This pull request adds a photo roll navigation panel to the preview app, allowing users to see thumbnails of all previewable files and navigate between them.

Key Changes:

• Modified the CachedFile type to make url an optional Vue ref for reactive preview URL updates
• Created a new PhotoRoll.vue component that displays a vertical thumbnail list with auto-scrolling to active items
• Updated the App.vue to integrate the photo roll, simplify preloading logic, and handle photo roll selection

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
packages/web-app-preview/src/helpers/types.ts	Changed url property from string to optional Vue ref for reactive preview URLs
packages/web-app-preview/src/components/PhotoRoll.vue	Added new photo roll component with thumbnail display and navigation
packages/web-app-preview/src/App.vue	Integrated photo roll component, updated URL handling to use refs, and simplified preloading logic

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[kulmann]

Woah, this is awesome guys! Really love it! 😍

Some tiny UX "issues":

• can I collapse / hide the photo roll somehow if I want to have more screen real estate for the image itself? maybe something for the control bar at the bottom?
• since the photo roll is vertical, I'd expect to be able to use to up and down arrow keys as well for navigation now (up and left both going to the previous image, down and right both going to the next image)
• when I have a wide screen the whitespace (grey) around the photo roll gets quite large... can we have a max width for that, so that the whitespace doesn't get so big (see screenshot)?

[kulmann]

Love it! Great idea 🥇

[tackin]

Please make it optional via env-var as it produces heavy load on Server-CPUs. Opencloud runs for months with loads up to 1.5 until now. But the use of the Photo-roll by a single user crashes the system and makes opencloud unusable for me on that computer.