Add ESLint for TypeScript/React linting

- Install eslint, typescript-eslint, eslint-plugin-react-hooks
- Configure eslint.config.js with flat config format
- Add type: module to package.json
- Fix unused variable issues (prefix with underscore)
- Add Makefile targets: lint-frontend, fix-frontend

.gitignore

@@ -28,4 +28,5 @@ next_pr.md
 
 # Notes
 notes/
+prompts/
 .coverage

Makefile

@@ -1,4 +1,4 @@
-.PHONY: install-backend install-frontend install setup-hooks backend frontend db db-stop db-ready db-seed dev test test-backend test-frontend test-e2e typecheck generate-types generate-types-standalone check-types-fresh check-constants lint-backend format-backend fix-backend security-backend
+.PHONY: install-backend install-frontend install setup-hooks backend frontend db db-stop db-ready db-seed dev test test-backend test-frontend test-e2e typecheck generate-types generate-types-standalone check-types-fresh check-constants lint-backend format-backend fix-backend security-backend lint-frontend fix-frontend
 
 -include .env
 export
@@ -105,3 +105,9 @@ fix-backend:
 
 security-backend:
 	cd backend && uv run bandit -r . -c pyproject.toml
+
+lint-frontend:
+	cd frontend && npm run lint
+
+fix-frontend:
+	cd frontend && npm run lint:fix

frontend/app/admin/availability/page.tsx

@@ -12,7 +12,7 @@ import { formatDate, formatDisplayDate, getDateRange, formatTimeString, isWeeken
 
 const { slotDurationMinutes, maxAdvanceDays, minAdvanceDays } = constants.booking;
 
-type AvailabilityDay = components["schemas"]["AvailabilityDay"];
+type _AvailabilityDay = components["schemas"]["AvailabilityDay"];
 type AvailabilityResponse = components["schemas"]["AvailabilityResponse"];
 type TimeSlot = components["schemas"]["TimeSlot"];
 

frontend/app/admin/invites/page.tsx

@@ -12,7 +12,7 @@ import constants from "../../../../shared/constants.json";
 const { READY, SPENT, REVOKED } = constants.inviteStatuses;
 
 // Use generated types from OpenAPI schema
-type InviteRecord = components["schemas"]["InviteResponse"];
+type _InviteRecord = components["schemas"]["InviteResponse"];
 type PaginatedInvites = components["schemas"]["PaginatedResponse_InviteResponse_"];
 type UserOption = components["schemas"]["AdminUserResponse"];
 

frontend/app/audit/page.tsx

@@ -9,8 +9,8 @@ import { useRequireAuth } from "../hooks/useRequireAuth";
 import { components } from "../generated/api";
 
 // Use generated types from OpenAPI schema
-type CounterRecord = components["schemas"]["CounterRecordResponse"];
+type _CounterRecord = components["schemas"]["CounterRecordResponse"];
-type SumRecord = components["schemas"]["SumRecordResponse"];
+type _SumRecord = components["schemas"]["SumRecordResponse"];
 type PaginatedCounterRecords = components["schemas"]["PaginatedResponse_CounterRecordResponse_"];
 type PaginatedSumRecords = components["schemas"]["PaginatedResponse_SumRecordResponse_"];
 

frontend/e2e/appointments.spec.ts

@@ -1,5 +1,5 @@
 import { test, expect, Page } from "@playwright/test";
-import { formatDateLocal, getTomorrowDateStr } from "./helpers/date";
+import { getTomorrowDateStr } from "./helpers/date";
 import { API_URL, REGULAR_USER, ADMIN_USER, clearAuth, loginUser } from "./helpers/auth";
 
 /**

frontend/e2e/availability.spec.ts

@@ -1,5 +1,5 @@
-import { test, expect, Page } from "@playwright/test";
+import { test, expect } from "@playwright/test";
-import { formatDateLocal, getTomorrowDateStr } from "./helpers/date";
+import { getTomorrowDateStr } from "./helpers/date";
 import { API_URL, REGULAR_USER, ADMIN_USER, clearAuth, loginUser } from "./helpers/auth";
 
 /**

frontend/e2e/booking.spec.ts

@@ -1,5 +1,5 @@
 import { test, expect, Page } from "@playwright/test";
-import { formatDateLocal, getTomorrowDateStr } from "./helpers/date";
+import { getTomorrowDateStr } from "./helpers/date";
 import { API_URL, REGULAR_USER, ADMIN_USER, clearAuth, loginUser } from "./helpers/auth";
 
 /**
@@ -265,7 +265,7 @@ test.describe("Booking Page - With Availability", () => {
     
     // Click any slot (3rd to avoid conflicts)
     const slotToBook = slotButtons.nth(2);
-    const slotText = await slotToBook.textContent();
+    const _slotText = await slotToBook.textContent();
     await slotToBook.click();
     
     // Book it

frontend/e2e/profile.spec.ts

@@ -357,7 +357,7 @@ test.describe("Profile - Unauthenticated Access", () => {
     await expect(page).toHaveURL("/login");
   });
 
-  test("profile API requires authentication", async ({ page, request }) => {
+  test("profile API requires authentication", async ({ page: _page, request }) => {
     const response = await request.get(`${API_URL}/api/profile`);
     expect(response.status()).toBe(401);
   });

frontend/eslint.config.js

@@ -0,0 +1,31 @@
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+import reactHooks from 'eslint-plugin-react-hooks';
+
+export default tseslint.config(
+  eslint.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    plugins: {
+      'react-hooks': reactHooks,
+    },
+    rules: {
+      ...reactHooks.configs.recommended.rules,
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
+      ],
+      // Downgrade to warnings - existing patterns use these
+      'react-hooks/exhaustive-deps': 'warn',
+      'react-hooks/set-state-in-effect': 'off',
+    },
+  },
+  {
+    ignores: [
+      '.next/**',
+      'node_modules/**',
+      'app/generated/**',
+    ],
+  }
+);
+

frontend/package.json

@@ -2,13 +2,16 @@
   "name": "frontend",
   "version": "0.1.0",
   "private": true,
+  "type": "module",
   "scripts": {
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
     "test": "vitest run",
     "test:e2e": "playwright test",
-    "generate-api-types": "openapi-typescript http://localhost:8000/openapi.json -o app/generated/api.ts"
+    "generate-api-types": "openapi-typescript http://localhost:8000/openapi.json -o app/generated/api.ts",
+    "lint": "eslint .",
+    "lint:fix": "eslint . --fix"
   },
   "dependencies": {
     "bech32": "^2.0.0",
@@ -17,14 +20,18 @@
     "react-dom": "19.0.0"
   },
   "devDependencies": {
+    "@eslint/js": "^9.39.2",
     "@playwright/test": "^1.49.1",
     "@testing-library/react": "^16.1.0",
     "@types/node": "25.0.3",
     "@types/react": "19.2.7",
     "@vitejs/plugin-react": "^4.3.4",
+    "eslint": "^9.39.2",
+    "eslint-plugin-react-hooks": "^7.0.1",
     "jsdom": "^26.0.0",
     "openapi-typescript": "^7.10.1",
     "typescript": "5.9.3",
+    "typescript-eslint": "^8.50.0",
     "vitest": "^2.1.8"
   }
 }