chore: add frontend .env.example and fix gitignore

- Update frontend/.gitignore to allow .env.example
- Create frontend/.env.example with correct API_URL format (/api/v1 suffix)
- Document production URL: https://api-dev.gohorsejobs.com/api/v1

frontend/.env.example

@@ -0,0 +1,15 @@
+# =============================================================================
+# GoHorse Jobs Frontend - Environment Variables Example
+# =============================================================================
+# Copy this file to .env.local and update the values
+
+# API Backend URL
+# IMPORTANT: Include /api/v1 suffix
+# Local development:
+NEXT_PUBLIC_API_URL=http://localhost:8521/api/v1
+
+# Production:
+# NEXT_PUBLIC_API_URL=https://api-dev.gohorsejobs.com/api/v1
+
+# Vercel Analytics (optional)
+NEXT_PUBLIC_VERCEL_ANALYTICS=false

frontend/.gitignore

@@ -30,8 +30,9 @@ yarn-debug.log*
 yarn-error.log*
 .pnpm-debug.log*
 
-# env files (can opt-in for committing if needed)
+# env files (keep .env.example for documentation)
 .env*
+!.env.example
 
 # vercel
 .vercel