Cleanup: extract constants, fix typecheck, add ESLint, organize store types

- Remove unused initCount state from useAuthGate hook
- Replace magic number with MAX_SAVES_PER_USER constant in saves route
- Extract duplicated EMAIL_REGEX and MIN_PASSWORD_LENGTH in auth routes
- Fix game-simulation typecheck failure by adding DOM lib to tsconfig
- Extract store UI types (ActivePage, InfraNav, etc.) to store/types.ts
- Fix let→const for non-reassigned arrays in servingPipeline
- Fix useless initial assignments in reputationSystem
- Fix ambiguous multiline array access in sanityChecks
- Add minimal ESLint config with typescript-eslint
- Add .planning/ and *.log to .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

eslint.config.mjs

@@ -0,0 +1,18 @@
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+
+export default tseslint.config(
+  eslint.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    ignores: ['**/dist/**', '**/node_modules/**', '**/*.js', '**/*.mjs', '**/drizzle/**'],
+  },
+  {
+    rules: {
+      '@typescript-eslint/no-unused-vars': ['warn', { argsIgnorePattern: '^_' }],
+      '@typescript-eslint/no-explicit-any': 'warn',
+      'no-empty': ['error', { allowEmptyCatch: true }],
+      'preserve-caught-error': 'off',
+    },
+  },
+);