🔧 Fix: Add DATABASE_URL runtime support for category pages

- Updated Dockerfile to accept DATABASE_URL at runtime
- Added .env.example for frontend
- Created Coolify environment setup guide

Fixes category pages 404 error - DATABASE_URL needs to be set in Coolify

COOLIFY-ENV-SETUP.md

@@ -0,0 +1,84 @@
+# Coolify Environment Variables Setup
+
+## Issue: Category Pages 404 Error
+
+**Root Cause:** DATABASE_URL environment variable not set in Coolify deployment
+
+## Solution
+
+### Set Environment Variable in Coolify
+
+1. Go to Coolify dashboard: https://coolify.qikbite.asia
+2. Navigate to Applications → burmddit
+3. Go to "Environment Variables" tab
+4. Add the following variable:
+
+```
+Name: DATABASE_URL
+Value: postgres://burmddit:Burmddit2026@172.26.13.68:5432/burmddit
+```
+
+5. Save and redeploy
+
+### Alternative: Via Coolify API
+
+```bash
+curl -X POST \
+  https://coolify.qikbite.asia/api/v1/applications/ocoock0oskc4cs00o0koo0c8/envs \
+  -H "Authorization: Bearer YOUR_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "key": "DATABASE_URL",
+    "value": "postgres://burmddit:Burmddit2026@172.26.13.68:5432/burmddit",
+    "is_build_time": false,
+    "is_preview": false
+  }'
+```
+
+## Dockerfile Changes Made
+
+Updated `/Dockerfile` to accept DATABASE_URL at runtime:
+
+```dockerfile
+# Production image
+FROM base AS runner
+WORKDIR /app
+
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+
+# Database URL will be provided at runtime by Coolify
+ARG DATABASE_URL
+ENV DATABASE_URL=${DATABASE_URL}
+```
+
+## Testing After Fix
+
+Once environment variable is set and redeployed:
+
+```bash
+# Test category pages
+curl https://burmddit.com/category/ai-news
+curl https://burmddit.com/category/tutorials
+curl https://burmddit.com/category/tips-tricks
+curl https://burmddit.com/category/upcoming
+```
+
+Should return HTML content with articles, not 404.
+
+## Files Modified
+
+1. ✅ `/Dockerfile` - Added runtime DATABASE_URL
+2. ✅ `/frontend/.env.example` - Documented required env vars
+3. ✅ `/COOLIFY-ENV-SETUP.md` - This file
+
+## Next Steps
+
+1. **Boss:** Set DATABASE_URL in Coolify (manual step - requires Coolify UI access)
+2. **Modo:** Push changes and trigger redeploy
+3. **Verify:** Test category pages after deployment
+
+---
+
+**Status:** ⏳ Waiting for environment variable to be set in Coolify
+**ETA:** ~5 minutes after env var is set and redeployed