Implement write endpoints as generic CRUD resources

[rikedyp]

Implement the redesigned REST write endpoints for the simple table resources: person, organisation, event, event_type, presentation_type, category. Might want one for every table.

Each gets three routes:

• POST /{resource} — create (insert)
• PATCH /{resource}/{id} — update
• DELETE /{resource}/{id} — delete

Refactor import.Table (currently a single upsert function) into separate create/update/delete handlers.

Decide on the :Hold 'SQL.db' lock: keep the global lock for now or narrow it per-table.

To do:

• POST/PATCH/DELETE routes
• OpenAPI request/response schemas attached
• Auth enforced on all write routes
• Database write lock prevents concurrent writes to the same table
• Create returns 201, Update returns 200, Delete returns 204