Backend Feature: UpdateInstitution

User story

As an admin, I want to update the institution's contact information, so that the website always shows up-to-date data.

Dependencies

• Entities: Institution
• API specs: Institution API

Acceptance criteria

• [ ] PATCH /institution updates only the fields provided in the request body.
• [ ] whatsapp is rejected if it contains any non-digit character.
• [ ] Returns 404 if no institution record exists.
• [ ] Returns the updated institution record on success.
• [ ] At least one field must be present in the body; empty body is rejected with 400.

Edge cases

• Request with no fields: return 400.
• whatsapp with spaces, dashes, or parentheses: return 400.
• Institution record not yet seeded: return 404.

Notes

• The institution is a singleton — the route has no ID parameter; it always targets the first (and only) non-deleted record.
• name and slug are not updatable through this endpoint.