fix: resolve YAML syntax errors in create-release workflow

Replaced heredocs with echo statements to avoid YAML parsing issues.
The YAML parser was interpreting markdown headings and other content
within heredocs as YAML syntax, causing validation errors.

Using grouped echo statements ({ echo ...; } > file) works correctly
with GitHub Actions YAML parser while maintaining variable expansion.

Also updated documentation to use generic placeholder (your-dockerhub-username)
in examples instead of hardcoded username.

docs/PREBUILT_IMAGES.md

@@ -48,11 +48,8 @@ cp .env.prebuilt .env
 Edit `.env` and set your Docker Hub username:
 
 ```bash
-# Change this line:
+# Change this line to your Docker Hub username:
 DOCKERHUB_USERNAME=your-dockerhub-username
-
-# To (example):
-DOCKERHUB_USERNAME=uprightbass360
 ```
 
 ### 4. Optional: Customize Settings

docs/RELEASES.md

@@ -145,7 +145,7 @@ cd azerothcore-realmmaster-v1.0.0-realmmaster
 
 # 3. Configure
 nano .env.prebuilt
-# Set: DOCKERHUB_USERNAME=uprightbass360
+# Set: DOCKERHUB_USERNAME=your-dockerhub-username
 
 # 4. Deploy
 mv .env.prebuilt .env