Add eslint flat-config for client and server and gate typecheck, lint and pages in CI

client and server had lint scripts but no eslint config (only shared was linted in CI). Add flat configs mirroring shared's stack (js + typescript-eslint recommended + eslint-config-prettier) plus the client's react-hooks/react-refresh plugins. Pre-existing patterns in this never-linted code (explicit any, require() in the CommonJS server, empty catches, exhaustive-deps) are set to 'warn' rather than 'error' so the gate passes at 0 errors without a repo-wide reformat — these can be ratcheted to errors over time. Wire blocking typecheck + lint + lint:pages steps into the client and server CI jobs (now that both typechecks are clean) and promote the server typecheck from informational to blocking.

server/eslint.config.mjs

@@ -0,0 +1,47 @@
+import js from '@eslint/js';
+
+import gitignore from 'eslint-config-flat-gitignore';
+import eslintConfigPrettier from 'eslint-config-prettier';
+import tseslint from 'typescript-eslint';
+
+export default tseslint.config(
+  gitignore({ strict: false }),
+  {
+    ignores: [
+      'node_modules',
+      'dist',
+      'coverage',
+      'public',
+      'data',
+      'uploads',
+      'assets',
+      'scripts/**',
+      'reset-admin.js',
+      '**/*.config.js',
+      '**/*.config.ts',
+      '**/*.config.mjs',
+    ],
+  },
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+  eslintConfigPrettier,
+  {
+    files: ['src/**/*.ts', 'tests/**/*.ts'],
+    rules: {
+      // --- Severities tuned to keep CI green on a codebase that was never linted ---
+      // (each rule below has pre-existing violations; surfaced as warnings, not blockers)
+      '@typescript-eslint/no-explicit-any': 'warn',
+      '@typescript-eslint/no-unused-vars': [
+        'warn',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_', caughtErrorsIgnorePattern: '^_' },
+      ],
+      // The server is CommonJS (tsconfig module: commonjs); require() is intentional throughout.
+      '@typescript-eslint/no-require-imports': 'warn',
+      '@typescript-eslint/no-unsafe-function-type': 'warn',
+      // js.recommended rules with pre-existing hits in the never-linted codebase.
+      'no-empty': 'warn',
+      'no-useless-escape': 'warn',
+      'prefer-const': 'warn',
+    },
+  },
+);

server/package.json

@@ -11,6 +11,7 @@
     "format": "prettier --write \"src/**/*.ts\" \"test/**/*.ts\"",
     "format:check": "prettier --check \"src/**/*.ts\" \"test/**/*.ts\"",
     "lint": "eslint \"{src,apps,libs,test}/**/*.ts\" --fix",
+    "lint:check": "eslint .",
     "test": "vitest run",
     "test:watch": "vitest",
     "test:unit": "vitest run tests/unit",
@@ -64,6 +65,7 @@
     "file-type": "^21.3.4"
   },
   "devDependencies": {
+    "@eslint/js": "^10.0.1",
     "@trivago/prettier-plugin-sort-imports": "^6.0.2",
     "eslint-config-prettier": "^10.0.1",
     "eslint-plugin-prettier": "^5.2.2",
@@ -71,6 +73,7 @@
     "prettier-plugin-organize-imports": "^4.3.0",
     "eslint": "^9.18.0",
     "eslint-config-flat-gitignore": "^2.3.0",
+    "typescript-eslint": "^8.58.2",
     "@nestjs/testing": "^11.1.24",
     "@swc/core": "^1.15.40",
     "@types/archiver": "^7.0.0",