Implement .comapeocat category set import flow (connect IndexedDB → UI)

[luandro]

Problem

The Import Category Set dialog was built (file upload, Valibot validation, duplicate detection, IndexedDB persistence) and the UI was wired into CategoriesEditorScreen in PR #147. However, the import flow is a dead end:

• importCategorySet() writes to a local IndexedDB (comapeo-categories Dexie DB)
• CategoriesEditorScreen reads categories from the server API via useApiPresets() (TanStack Query → GET /projects/:id/presets)
• These two data sources are not connected — nothing reads from IndexedDB
• After import shows "success", the category list doesn't change
• No queryClient.invalidateQueries() is called

The Import button and dialog have been commented out in CategoriesEditorScreen and its tests until the full flow is implemented.

What exists (keep + build on)

• src/screens/CategoriesEditor/ImportSetDialog.tsx — full dialog UI (317 lines)
• src/lib/categories-db.ts — IndexedDB layer (78 lines): importCategorySet(), getCategorySets(), getCategorySet()
• src/lib/schemas/preset.ts — comapeoCatSchema Valibot schema
• i18n keys in all 3 locales (en/pt/es): categories.importSet.*, categories.importButton

What needs to happen

Decide on architecture before implementing:

Option A: Client-side bridge (offline-capable)

• Create a useCategorySets() hook that reads from IndexedDB
• Merge IndexedDB sets with server presets in CategoriesEditorScreen
• Invalidate/refetch the hook after import
• More complex, handles offline scenarios

Option B: Server-side import (single source of truth)

• Upload .comapeocat file to the comapeo-cloud API
• Server imports + stores the category set
• queryClient.invalidateQueries(['presets']) after successful upload
• Simpler architecture, but depends on server API support

Acceptance Criteria

• User can upload a .comapeocat file via the Import Category Set dialog
• After successful import, the imported categories appear in the category grid
• Imported categories persist across page reloads
• Replace-existing confirmation works end-to-end
• Re-enable the commented-out UI in CategoriesEditorScreen + tests
• Add integration test verifying the full import → render flow

Context

• PR feat: Categories Editor — browse, search, and view preset category sets (closes #143) #147: initial Categories Editor implementation
• PR branch: agent/comapeo-cloud-app/issue-143
• Files commented out: src/screens/CategoriesEditor/index.tsx (Import button + dialog render), tests/unit/screens/CategoriesEditor/index.test.tsx (2 import dialog tests)