feat: connect practice workspace with contacts, calendar and billing

[Strudelcode]

Summary

• align the Practice/Therapy icon with the App Store and launcher using the professional Briefcase icon
• use the existing shared Contacts list when creating clients
• create therapy appointments in the shared local calendar and refresh the Calendar module immediately
• route Practice billing into the existing invoice workflow and show real invoices in the billing tab
• add EN/DE/FR/ES translations for the integration workflow
• store Practice/Therapy data per signed-in SOCDOF user in IndexedDB
• automatically create rolling per-user backups (last 10 snapshots) on saves, instead of relying on manual file export
• migrate the legacy shared Therapy localStorage record into the active user's new store and remove the shared legacy key

Scope

This PR targets main but is intentionally opened as a draft for review/merge coordination. No changes have been pushed directly to main.

Verification

• GitHub Actions is expected to run npm run lint and npm run build on this PR.
• CI status is currently not reported for the latest head commit yet.
• Local build could not be executed from this environment because outbound GitHub network access is unavailable.