feat: Add animation effect for navigation entries

[jancborchardt]

Assisted-by: ClaudeCode:claude-opus-4-8

☑️ Resolves

It would be nice to have an animation of the hover feedback highlight of the NcAppNavigation. This makes it feel nicer and smoother, like you are actually interacting with something.

This is a prototype to see how that could look like. Has been tested in the styleguide.
@susnux @ShGKme please check if this would this be good as a base, or should take a different approach.

nextcloud/server#61621 adds global handling for the animation-quick and animation-slow variables to be zeroed under prefers-reduced-motion.

🖼️ Screenshots

🏚️ Before

Screencast.From.2026-06-27.01-40-20.webm

🏡 After

Screencast.From.2026-06-27.01-34-40.webm

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[codecov]

Codecov Report

❌ Patch coverage is 1.38889% with 71 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.97%. Comparing base (f54323d) to head (47d32da).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
...onents/NcAppNavigationList/NcAppNavigationList.vue	1.38%	59 Missing and 12 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8685      +/-   ##
==========================================
- Coverage   54.06%   52.97%   -1.10%     
==========================================
  Files         106      106              
  Lines        3479     3549      +70     
  Branches     1008     1022      +14     
==========================================
- Hits         1881     1880       -1     
- Misses       1354     1413      +59     
- Partials      244      256      +12     

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[susnux]

I do not see anything in the "after" screencast that requires JS changes, that should be possible with pure CSS so no heavy mutation observer is required, no?