Add ESLint with CI enforcement

.github/workflows/ci.yml

@@ -40,3 +40,20 @@ jobs:
             echo "::error::Please run pip-compile to regenerate lockfiles. See README for instructions."
             exit 1
           fi
+
+  frontend-lint:
+    name: Frontend Lint & Typecheck
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: frontend
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+      - run: npm ci
+      - run: npm run lint
+      - run: npm run typecheck

README.md

@@ -36,10 +36,17 @@ Services start automatically with hot reload:
 
 ### Testing
 ```bash
-npm run lint                # Frontend linting (in frontend directory)
+# Via Docker (recommended)
+docker compose -f docker-compose.dev.yml exec frontend npm run lint
+docker compose -f docker-compose.dev.yml exec frontend npm run typecheck
+
+# Or locally in the frontend directory
+npm run lint                # ESLint (must pass with zero errors)
 npm run typecheck           # TypeScript type checking
 ```
 
+Both checks run in CI on pushes to `main` and on pull requests.
+
 ### Populating Mock Data
 ```bash
 docker compose -f docker-compose.dev.yml exec backend python scripts/populate_db.py

docker-README.md

@@ -152,6 +152,16 @@ ADMIN_GITHUB_TEAMS=memory-python-org
 
 **Note:** Development compose file uses port 9002 for frontend, production uses 3000.
 
+### Linting & Type Checking
+
+```bash
+# ESLint (must pass with zero errors)
+docker compose -f docker-compose.dev.yml exec frontend npm run lint
+
+# TypeScript type checking
+docker compose -f docker-compose.dev.yml exec frontend npm run typecheck
+```
+
 ### Accessing the Database
 
 ```bash