Add root .env.example for Docker Compose configuration

.env.example

@@ -0,0 +1,33 @@
+# Docker Compose Environment Variables
+# Copy this file to .env and customize for your setup
+
+# Backend Secret Key (CHANGE THIS!)
+# Generate with: openssl rand -hex 32
+SECRET_KEY=your-super-secret-key-change-this-in-production
+
+# Application Settings
+DEBUG=True
+APP_NAME=Family Hub
+APP_VERSION=0.1.0
+
+# Database
+DATABASE_URL=sqlite:///./family_hub.db
+
+# CORS Settings
+ALLOWED_ORIGINS=http://localhost:5173,http://localhost:3000
+
+# JWT Settings
+ACCESS_TOKEN_EXPIRE_MINUTES=30
+
+# Optional: Google Calendar Integration (Phase 3)
+# GOOGLE_CLIENT_ID=
+# GOOGLE_CLIENT_SECRET=
+# GOOGLE_REDIRECT_URI=
+
+# Optional: Mealie Integration (Phase 4)
+# MEALIE_API_URL=
+# MEALIE_API_TOKEN=
+
+# Optional: Home Assistant Integration (Phase 6)
+# HOME_ASSISTANT_URL=
+# HOME_ASSISTANT_TOKEN=