Add ESLint + Prettier + EditorConfig tooling at repo root

v1.0 Phase 1.1 — repo-wide lint/format baseline.

- eslint.config.mjs (flat config) lints server, client, shared
- .prettierrc.json, .prettierignore, .editorconfig, .nvmrc
- Root package.json holds shared devDeps; per-package scripts keep
  their typecheck + test runners
- Fix 7 lint issues surfaced by the baseline run:
  - TicketDetail.tsx: replace ternary-with-side-effects with if/else
  - admin/Users.tsx: escape apostrophe in JSX
  - errorHandler.ts: typed err as unknown with ErrorLike refinement
  - users.ts: Prisma.UserUpdateInput instead of Record<string, any>
  - seed.ts: drop unused goddard binding
- Run prettier across tracked sources for a clean formatting baseline

eslint.config.mjs

@@ -0,0 +1,78 @@
+import js from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import react from 'eslint-plugin-react';
+import reactHooks from 'eslint-plugin-react-hooks';
+import globals from 'globals';
+
+export default [
+  {
+    ignores: [
+      '**/dist/**',
+      '**/node_modules/**',
+      '**/.vite/**',
+      '**/coverage/**',
+      'server/prisma/migrations/**',
+      'client/src/components/ui/**',
+    ],
+  },
+
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+
+  {
+    files: ['client/src/**/*.{ts,tsx}'],
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: 'module',
+      globals: { ...globals.browser },
+      parserOptions: {
+        ecmaFeatures: { jsx: true },
+      },
+    },
+    plugins: {
+      react,
+      'react-hooks': reactHooks,
+    },
+    settings: {
+      react: { version: 'detect' },
+    },
+    rules: {
+      ...react.configs.recommended.rules,
+      ...reactHooks.configs.recommended.rules,
+      'react/react-in-jsx-scope': 'off',
+      'react/prop-types': 'off',
+      '@typescript-eslint/no-unused-vars': [
+        'warn',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
+      ],
+      '@typescript-eslint/no-explicit-any': 'warn',
+    },
+  },
+
+  {
+    files: ['server/src/**/*.ts', 'server/prisma/**/*.ts'],
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: 'module',
+      globals: { ...globals.node },
+    },
+    rules: {
+      '@typescript-eslint/no-unused-vars': [
+        'warn',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
+      ],
+      '@typescript-eslint/no-explicit-any': 'warn',
+    },
+  },
+
+  {
+    files: ['shared/**/*.ts'],
+    languageOptions: {
+      ecmaVersion: 2022,
+      sourceType: 'module',
+    },
+    rules: {
+      '@typescript-eslint/no-unused-vars': ['warn', { argsIgnorePattern: '^_' }],
+    },
+  },
+];