Simplify / Componentize LAMB Frontend

[juananpe]

The main LAMB frontend consists of overly large Svelte files. For example, frontend/svelte-app/src/routes/org-admin/+page.svelte (accessible at http://localhost:9099/org-admin?view=bulk-import) has over 4,400 lines.

We should refactor these files by extracting reusable components. We also need to remove dead code - for instance, the file mentioned above contains unused code related to BulkUserImport.

These oversized files complicate development and debugging, and make it difficult for AI coding agents to work with them effectively.

[granludo]

working on it on svelte-refactor branch