Add joule-studio and 3 active tutorial groups to repository-groups.json

[jung-thomas]

Adds four repository groups to config/repository-groups.json:

name	note
joule-studio	New group requested for the SAGE authoring extension (issue #50 there).
datasphere-skills-club	Existing active repo, was missing from this config.
sap-conversational-ai	Existing active repo, was missing from this config.
sap-mobile-cards	Existing active repo, was missing from this config.

Why

The SAGE VS Code authoring extension is moving to discover repository groups dynamically from this file (instead of a list hardcoded in the extension). For that to be a clean, additive change, this config needs to be the single source of truth. joule-studio is new; the other three already exist as sap-tutorials/* repositories and were selectable in the extension's old hardcoded list but absent here — adding them prevents them from disappearing once the extension goes config-driven.

Each entry follows the existing schema (name, description, urlBase, teamAdmin) and includes a human-readable description. Validated as well-formed JSON (25 entries total).

[sap-tutorials-builder]

✅ No issues found

Checked a1ff216 • notify-only, does not block merge