Improve build system and clean up project structure

- Configure build script to create backups in backup/ directory
- Add backup/ directory to .gitignore to keep repo clean
- Add .gitignore file with common exclusions
- Remove obsolete dog-food-calculator-widget.js file
- Move all temporary and reference files to sundog-calculator-meta/

This keeps the project root clean and organized while maintaining
automatic backups during builds.

.gitignore

@@ -0,0 +1,27 @@
+# Dependencies
+node_modules/
+
+# IDE
+.vscode/
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Temporary files
+*.tmp
+*.temp
+
+# Personal files
+theme.scss
+_variables.scss
+reference.png
+better.png
+START_PROMPT.md
+CLAUDE.md
+CLAUDE_V2.md
+math.md
+vetcalculators/
+*.js.backup*
+backup/

build.js

@@ -77,14 +77,21 @@ function readSourceComponents() {
  * Backup existing files
  */
 function backupFiles() {
+    const backupDir = 'backup';
+    
+    // Create backup directory if it doesn't exist
+    if (!fs.existsSync(backupDir)) {
+        fs.mkdirSync(backupDir);
+    }
+    
     const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
     const filesToBackup = ['iframe.html', 'sundog-dog-food-calculator.js'];
     
     filesToBackup.forEach(file => {
         if (fs.existsSync(file)) {
-            const backupName = `${file}.backup-${timestamp}`;
+            const backupName = path.join(backupDir, `${file}.backup-${timestamp}`);
             fs.copyFileSync(file, backupName);
-            console.log(`📦 Backed up ${file} to: ${backupName}`);
+            console.log(`   📦 Backed up ${file}`);
         }
     });
 }