refactor: improve type safety and revamp api client

[jcscottiii]

Refactored the frontend to use stricter typing and path-aware response handling. Replaced unsafe type assertions with type guards and updated the API client to handle specific status codes more robustly.

• Reorganized api/client.ts to use status code handlers per endpoint
• Added type guards for saved searches and vendor positions
• Cleaned up manual casts and redundant checks across components
• Fixed various linting and formatting issues to match project standards

Rules that are enabled now:

      '@typescript-eslint/no-explicit-any': 'error',
      '@typescript-eslint/no-unsafe-type-assertion': 'error',
      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
      '@typescript-eslint/no-restricted-types': [
        'error',
        {
          types: {
            unknown:
              'Prefer explicit types or type guards instead of unknown. Use unknown only in tests or where absolutely unavoidable.',
          },
        },
      ],

This prevents the use of any, as type casting and unknown