Migrate existing locations to new location management system

[achildrenmile]

Background

Existing locations are currently defined using the legacy approach in the repository.
With the introduction of a new admin cockpit, API, and persistent storage, these locations must not be lost.

Description

Ensure that all currently existing locations are transferred into the new location management solution.

Scope

• Analyze how locations are currently stored/defined
• Define a target data model compatible with the new database
• Migrate existing location data into the new storage (e.g. SQLite)
• Validate migrated data for correctness and completeness

Tasks

• Identify all existing locations in the current codebase
• Implement a one-time migration script or import mechanism
• Verify that frontend/API output matches previous behavior

Acceptance Criteria

• All existing locations are available in the new system
• No manual re-entry of location data required
• Frontend displays locations exactly as before
• Migration approach is documented

Notes

Migration should be reproducible and safe.
Ideally, it can be re-run in case of clean deployments (e.g. Docker).