Elastic: Show contact photo in recipient autocomplete list

[listumps]

Summary

• Shows the contact's vCard photo instead of the generic person icon in the To/Cc/Bcc recipient autocomplete dropdown when composing, when a photo is available.
• The photo is already parsed on every autocomplete search (rcube_contacts::search() always reads the vCard), so this adds no extra query cost - autocomplete.php just exposes a URL to the existing contacts/photo action per matching contact.
• Photos stored as external http(s):// URLs are intentionally excluded: contacts/photo.php 302-redirects the browser to those, and attaching one here would fire a silent third-party request on every keystroke for any matching contact, rather than only when a contact/email is deliberately opened.
• Both ksearch_results_display() in app.js and Elastic's own override of it in ui.js (used for its small-screen layout) needed updating, since the skin's override completely replaces the base implementation.
• The photo is capped to the existing .listing row height (@listing-line-height) and keeps its natural aspect ratio rather than being cropped to a circle, consistent with how photos are shown elsewhere in the app (Contacts page, sender photo in message preview).
• Contacts without a photo, and group/distribution-list entries, keep the existing icon unchanged.

Test plan

• Verified via php -l and the project's .php-cs-fixer.dist.php config (0 fixable issues) for autocomplete.php
• Verified via eslint (project config) for app.js and ui.js
• Verified the .less change compiles cleanly via lessc against the full styles.less entry point
• Manually tested end-to-end on a live instance: composing a message and searching for a contact with a vCard photo shows the photo in the dropdown; contacts without a photo and group entries still show the default icon
• Automated test coverage - none added; happy to add if maintainers want it

[listumps]

Removed the CHANGELOG.md entry from this PR, following the guidance given to @MiMoHo on another PR (changelog entries create unnecessary merge conflicts between PRs). Force-pushed the amended commit - PR now only touches the 4 code files.