chore: add example env file, improve documentation and code comments

example.env

@@ -0,0 +1,27 @@
+# Example environment variables for dlseitz.dev backend
+# DO NOT PUT REAL CREDENTIALS IN HERE
+# DO NOT COMMIT ACTUAL .env FILES TO VERSION CONTROL
+
+# Database-related
+#-----------------
+DB_HOST=your_database_host
+DB_PORT=5432
+DB_USER=your_database_user
+DB_PASSWORD=your_database_password
+DB_NAME=your_database_name
+
+# Email-related
+#--------------
+EMAIL_HOST=smtp.yourmail.com
+EMAIL_PORT=587
+EMAIL_USER=your_email_username
+EMAIL_PASS=your_email_password
+EMAIL_RCPT=recipient@example.com
+
+# Security-related
+#-----------------
+HCAPTCHA_SECRET=your_hcaptcha_secret_key
+
+# Other
+#------
+NODE_ENV=production