refactor: migrate to modular tool-based architecture

- Implement tool registry system with individual tool modules
- Reorganize transformers into categorized source modules
- Remove emojiLibrary.js, consolidate into EmojiUtils and emojiData
- Fix mobile close button and tooltip functionality
- Add build system for transforms and emoji data
- Migrate from Python backend to pure JavaScript
- Add comprehensive documentation and testing
- Improve code organization and maintainability
- Ignore generated files (transforms-bundle.js, emojiData.js)

src/transformers/encoding/hex.js

@@ -0,0 +1,40 @@
+// hex transform
+import BaseTransformer from '../BaseTransformer.js';
+
+export default new BaseTransformer({
+    name: 'Hexadecimal',
+    priority: 290,
+    // Detector: Only hex characters (0-9, A-F)
+    detector: function(text) {
+        const cleaned = text.trim().replace(/\s/g, '');
+        return cleaned.length >= 4 && /^[0-9A-Fa-f]+$/.test(cleaned);
+    },
+    
+    func: function(text) {
+            // Use TextEncoder to properly handle UTF-8 (including emoji)
+            const encoder = new TextEncoder();
+            const bytes = encoder.encode(text);
+            return Array.from(bytes).map(b => b.toString(16).padStart(2, '0')).join(' ');
+        },
+        preview: function(text) {
+            if (!text) return '[hex]';
+            const full = this.func(text);
+            return full.substring(0, 20) + (full.length > 20 ? '...' : '');
+        },
+        reverse: function(text) {
+            const hexText = text.replace(/\s+/g, '');
+            const bytes = [];
+            
+            for (let i = 0; i < hexText.length; i += 2) {
+                const byte = hexText.substr(i, 2);
+                if (byte.length === 2) {
+                    bytes.push(parseInt(byte, 16));
+                }
+            }
+            
+            // Use TextDecoder to properly decode UTF-8
+            const decoder = new TextDecoder('utf-8');
+            return decoder.decode(new Uint8Array(bytes));
+        }
+
+});