Add coordinate validation and ESLint integration

- Add explicit latitude/longitude validation in location submissions
- Implement ESLint with TypeScript support and flat config
- Auto-fix 621 formatting issues across codebase
- Add comprehensive tests for coordinate validation
- Update documentation with lint scripts and validation rules
- Maintain 128 passing tests with enhanced security

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/models/Location.test.ts

@@ -138,7 +138,7 @@ describe('Location Model', () => {
 
       // Check that we have all locations and they're ordered by created_at DESC
       expect(allLocations).toHaveLength(3);
-      
+
       // The query uses ORDER BY created_at DESC, so the most recent should be first
       // Since they're created in the same moment, check that ordering is consistent
       expect(allLocations[0]).toHaveProperty('id');