feat(contacts): admin-defined custom property types via app config

[fberke]

Summary

Allows admins to define custom property types (custom fields) for the contact editor via app config — no UI, a single occ command:

occ config:app:set contacts customProperties --value='[
  {"name": "x-customernumber", "label": "Customer number"},
  {"name": "x-region", "label": "Region", "force": "select",
   "options": [{"id": "NORTH", "name": "North"}, {"id": "SOUTH", "name": "South"}]}
]'

The fields show up in the "Add more info" menu and in the contact details, read-only and merge views like built-in fields, and are stored as regular X-… vCard properties, so they survive sync with other CardDAV clients.

Implements the config-based flavor of #3273 / #303.

How it works

• A new CustomPropertiesService reads and validates the customProperties app config (JSON). Only x-… property names are accepted; invalid entries are dropped and logged, so a broken config can never break the app. The config schema is documented in the class docblock.
• PageController provides the sanitized list as initial state.
• The frontend merges the entries into the rfcProps registry at boot (src/models/customProperties.js), so all existing views pick them up without further changes.

Supported keys per entry: label, force (text, default, or select), options (TYPE parameter choices for text fields, value choices for select fields), multiple, primary, icon.

Notes / limitations

• Labels are shown as configured (not translated) — they are admin-provided, instance-specific strings.
• Editor types are limited to text and select for now.
• Entries colliding with built-in property names are skipped.

Testing

• Unit tests for the service (validation matrix) and the frontend merge function; PageControllerTest updated for the new constructor dependency.
• Manually tested on Nextcloud 35.0.0 beta 4: fields appear in the editor, values round-trip through save/reload and appear in the vCard export as X-… properties.

🤖 Generated with Claude Code

[SebastianKrupinski]

Hi @fberke

Thank you for the PR. I had a quick look at the code, and noticed one thing, we require that any newly created front end files be created in typescript.

[fberke]

Thanks for the quick look! Fair point — I converted src/models/customProperties.js and its test to TypeScript in bc86685, typed against the config schema. Kept it as a fixup commit for now; I'll squash once the review is through.