Refactor symbols app: cleanup and fix issues

- Removed duplicate files (index2/3/4.html, symbols.js duplicates)
- Kept index4.html as the main index.html (modular version)
- Removed old text-generator.js (replaced by modular version)
- Fixed ID mismatch in ui-bindings.js to match HTML
- Added square and circle shape support in svg-generator.js
- Added legend preview with copy functionality
- Removed 580 lines of obsolete text-generator v4 code from app.js
- Added addTextToLegend and addStandaloneArrowToLegend to export.js

Still TODO: Split large files to comply with 300 line limit
- app.js: 1219 lines
- styles.css: 1319 lines
- symbols.js: 870 lines

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

symbols/js/text-generator/svg-generator.js

@@ -44,9 +44,19 @@ var SvgGenerator = {
             case 'rect':
                 shapeEl = draw.rect(width, height).move(x, y).radius(4);
                 break;
+            case 'square':
+                var squareSize = Math.max(width, height);
+                var squareX = x - (squareSize - width) / 2;
+                var squareY = y - (squareSize - height) / 2;
+                shapeEl = draw.rect(squareSize, squareSize).move(squareX, squareY).radius(4);
+                break;
             case 'rounded':
                 shapeEl = draw.rect(width, height).move(x, y).radius(Math.min(halfW, halfH) * 0.5);
                 break;
+            case 'circle':
+                var circleRadius = Math.max(halfW, halfH);
+                shapeEl = draw.circle(circleRadius * 2).center(cx, cy);
+                break;
             case 'oval':
                 shapeEl = draw.ellipse(width, height).center(cx, cy);
                 break;