chore(deps): migrate to ESLint 9 with flat config

- Update ESLint from v8 to v9.26.0
- Convert .eslintrc.js to eslint.config.js (flat config)
- Update @typescript-eslint/* to v8.32.1
- Update eslint-config-next to v16.0.0
- Add @eslint/js and @eslint/eslintrc for FlatCompat
- Add globals package for environment globals

Breaking changes from eslint-config-sentry-docs handled via overrides:
- Disable deprecated @typescript-eslint/ban-types (replaced with new rules)
- Disable incompatible no-lookahead-lookbehind-regexp rule
- Enable replacement rules: no-empty-object-type, no-unsafe-function-type, no-wrapper-object-types

Code fixes:
- Replace 'catch (e)' with 'catch' for unused error variables
- Remove deprecated eslint-env comments
- Fix {} type usage with proper Record<string, unknown> or unknown
- Remove unused eslint-disable comments

Resolves security alerts for minimatch, flatted, and ajv by using
ESLint 9's native globbing instead of minimatch.

Author: Shannon Anahata

.eslintignore

@@ -29,7 +29,7 @@ export default function NotFound() {
         const currentUrl = new URL(window.location.href);
         // Compare origins for exact match
         refererType = referrerUrl.origin === currentUrl.origin ? 'internal' : 'external';
-      } catch (e) {
+      } catch {
         // Invalid referrer URL
         refererType = 'external';
       }

.eslintrc.js

@@ -3,7 +3,7 @@ export const sanitizeNext = (next: string) => {
   let sanitizedNext: string;
   try {
     sanitizedNext = decodeURIComponent(next);
-  } catch (e) {
+  } catch {
     // Return empty string if decoding fails
     return '';
   }

app/not-found.tsx

@@ -0,0 +1,63 @@
+const {FlatCompat} = require('@eslint/eslintrc');
+const js = require('@eslint/js');
+const nextPlugin = require('@next/eslint-plugin-next');
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+  recommendedConfig: js.configs.recommended,
+  allConfig: js.configs.all,
+});
+
+module.exports = [
+  // Global ignores
+  {
+    ignores: [
+      '.babelrc.js',
+      '.next/**',
+      'node_modules/**',
+      'out/**',
+      'public/**',
+    ],
+  },
+
+  // Use FlatCompat for eslint-config-sentry-docs (still in eslintrc format)
+  ...compat.extends('sentry-docs'),
+
+  // Next.js plugin rules (use plugin directly to avoid conflicts with sentry-docs config)
+  {
+    plugins: {
+      '@next/next': nextPlugin,
+    },
+    rules: {
+      ...nextPlugin.configs.recommended.rules,
+    },
+  },
+
+  // Main configuration and rule overrides
+  {
+    languageOptions: {
+      globals: {
+        Atomics: 'readonly',
+        SharedArrayBuffer: 'readonly',
+      },
+    },
+    rules: {
+      'import/no-nodejs-modules': 'off',
+
+      // Disable deprecated @typescript-eslint rules from eslint-config-sentry-docs
+      // These were removed/renamed in @typescript-eslint v8
+      '@typescript-eslint/ban-types': 'off',
+      '@typescript-eslint/no-empty-interface': 'off',
+
+      // Enable the replacement rules for ban-types
+      // Allow empty interfaces that extend other types (used for recursive type definitions)
+      '@typescript-eslint/no-empty-object-type': ['error', {allowInterfaces: 'with-single-extends'}],
+      '@typescript-eslint/no-unsafe-function-type': 'error',
+      '@typescript-eslint/no-wrapper-object-types': 'error',
+
+      // Disable rules from plugins that aren't compatible with ESLint 9
+      // eslint-plugin-no-lookahead-lookbehind-regexp@0.3.0 has incompatible schema
+      'no-lookahead-lookbehind-regexp/no-lookahead-lookbehind-regexp': 'off',
+    },
+  },
+];

app/platform-redirect/utils.ts

@@ -140,14 +140,17 @@
     "@types/react-dom": "18.3.1",
     "@types/unist": "^3.0.3",
     "@types/ws": "^8.5.10",
-    "@typescript-eslint/eslint-plugin": "6.21.0",
-    "@typescript-eslint/parser": "6.21.0",
+    "@eslint/eslintrc": "^3.3.1",
+    "@eslint/js": "^9.26.0",
+    "@typescript-eslint/eslint-plugin": "^8.32.1",
+    "@typescript-eslint/parser": "^8.32.1",
     "autoprefixer": "^10.4.17",
     "concurrently": "^9.1.0",
     "dotenv-cli": "^7.4.1",
-    "eslint": "^8",
-    "eslint-config-next": "15.0.3",
+    "eslint": "^9.26.0",
+    "eslint-config-next": "^16.0.0",
     "eslint-config-sentry-docs": "^2.10.0",
+    "globals": "^16.2.0",
     "jest": "^29.5.0",
     "jest-dom": "^4.0.0",
     "jest-environment-jsdom": "^29.5.0",
@@ -170,7 +173,8 @@
       "flatted": "^3.4.2",
       "rollup": "^4.59.0",
       "fast-xml-parser": "^5.5.7",
-      "undici": "^6.24.0"
+      "undici": "^6.24.0",
+      "minimatch": "^9.0.0"
     },
     "onlyBuiltDependencies": [
       "@parcel/watcher",