Update: Checkout actions to v5

Checkout Action Upgrade:
- Replace all checkout actions with 'actions/checkout@v5'
- Latest version with improved performance and features
- Better compatibility with modern Git workflows
- Enhanced security and reliability

 Updated Workflows:
- CI Pipeline: All checkout actions  v5
- Security Scans: All checkout actions  v5
- Release Pipeline: All checkout actions  v5
- Documentation: All checkout actions  v5

 Benefits:
- Latest checkout action features
- Improved performance and caching
- Better error handling and logging
- Enhanced Git LFS support
- Modern Node.js runtime compatibility

 All 4 workflow files updated consistently

.gitea/workflows/docs.yml

@@ -26,7 +26,7 @@ jobs:
     
     steps:
     - name: Checkout code
-      uses: https://gitea.com/actions/checkout
+      uses: actions/checkout@v5
       
     - name: Set up Python
       uses: actions/setup-python@v4
@@ -126,7 +126,7 @@ jobs:
     
     steps:
     - name: Checkout code
-      uses: https://gitea.com/actions/checkout
+      uses: actions/checkout@v5
       
     - name: Set up Python
       uses: actions/setup-python@v4
@@ -223,7 +223,7 @@ jobs:
     
     steps:
     - name: Checkout code
-      uses: https://gitea.com/actions/checkout
+      uses: actions/checkout@v5
       
     - name: Set up Python
       uses: actions/setup-python@v4
@@ -248,8 +248,8 @@ jobs:
         project = 'Northern Thailand Ping River Monitor'
         copyright = '2025, Ping River Monitor Team'
         author = 'Ping River Monitor Team'
-        version = '3.1.1'
-        release = '3.1.1'
+        version = '3.1.2'
+        release = '3.1.2'
         
         extensions = [
             'sphinx.ext.autodoc',