Add TS rule to enforce thrown errors to be an instance of Error

**Context**
- If an error is thrown as string, the line number is not shown:
- Reference: https://github.com/bcgov/SIMS/pull/2753

**Acceptance Criteria**
- [ ] Apply TS rules as in: https://typescript-eslint.io/rules/no-throw-literal/
- [ ] Check if there's still any place throwing error as string.

Start with the typescript-eslint no-throw-literal rule linked in the acceptance criteria and review reference pull request #2753. Search the TypeScript codebase for locations that throw strings, enable or apply the rule, and confirm the lint check passes with no remaining string throws.

Written by the indexing model from the issue text.