Add coordinate validation and ESLint integration

- Add explicit latitude/longitude validation in location submissions
- Implement ESLint with TypeScript support and flat config
- Auto-fix 621 formatting issues across codebase
- Add comprehensive tests for coordinate validation
- Update documentation with lint scripts and validation rules
- Maintain 128 passing tests with enhanced security

🤖 Generated with [Claude Code](https://claude.ai/code)

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

README.md

@@ -6,10 +6,11 @@ A community-driven web application for tracking winter road conditions and icy h
 
 - 🗺️ **Interactive Map** - Real-time location tracking centered on Grand Rapids
 - ⚡ **Fast Geocoding** - Lightning-fast address lookup with MapBox API
-- 🔄 **Auto-Expiration** - Reports automatically removed after 24 hours
+- 🔄 **Auto-Expiration** - Reports automatically removed after 48 hours
 - 👨‍💼 **Admin Panel** - Manage and moderate location reports
 - 📱 **Responsive Design** - Works on desktop and mobile devices
 - 🔒 **Privacy-Focused** - No user tracking, community safety oriented
+- 🛡️ **Enhanced Security** - Coordinate validation, rate limiting, and content filtering
 
 ## Quick Start
 
@@ -39,11 +40,31 @@ A community-driven web application for tracking winter road conditions and icy h
 
 4. **Start the server:**
    ```bash
-   npm start          # Production mode
-   npm run dev        # Development mode
-   npm run dev-with-css  # Development with CSS watching
+   npm start              # Production mode
+   npm run dev            # Development mode
+   npm run dev-with-css   # Development with CSS watching
    ```
 
+## Development Commands
+
+### Code Quality
+```bash
+# Run ESLint to check code style and quality
+npm run lint
+
+# Auto-fix ESLint issues where possible
+npm run lint:fix
+```
+
+### Testing
+```bash
+# Run all tests (128+ tests with TypeScript)
+npm test
+
+# Run tests with coverage report (76% overall coverage)
+npm run test:coverage
+```
+
 5. **Visit the application:**
    ```
    http://localhost:3000
@@ -139,7 +160,7 @@ Interactive API documentation available at `/api-docs` when running the server.
 - **Frontend:** Vanilla JavaScript, Leaflet.js
 - **Geocoding:** MapBox API (with Nominatim fallback)
 - **Security:** Rate limiting, input validation, authentication
-- **Testing:** Jest, TypeScript, 125+ tests with 76% coverage
+- **Testing:** Jest, TypeScript, 128+ tests with 76% coverage
 - **Reverse Proxy:** Caddy (automatic HTTPS)
 - **Database:** SQLite (lightweight, serverless)
 
@@ -165,6 +186,8 @@ Interactive API documentation available at `/api-docs` when running the server.
 ### Input Limits
 - **Address:** Maximum 500 characters
 - **Description:** Maximum 1000 characters
+- **Latitude:** Must be between -90 and 90 degrees
+- **Longitude:** Must be between -180 and 180 degrees
 - **Submissions:** 10 per 15 minutes per IP address
 
 ## License