[FEATURE] - Migrate client to ESLint 10 #185

Problem to solve

Dependabot #172 (eslint 8.57 → 10.11) fails npm run lint: client/eslint.config.js imports @eslint/js and globals, which were only available transitively through ESLint 8 and are not declared in client/package.json. ESLint 10 no longer ships them.

Impact

Low

Proposed solution

Per ADR-004, migrate instead of holding back: bump eslint to 10.x, declare @eslint/js and globals as explicit devDependencies, fix any rule changes surfaced by npm run lint, then close #172 as superseded.

Constraints or notes

Client-only, devDependencies only; no runtime impact.