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)

templates/tokenizer.html

@@ -0,0 +1,48 @@
+<div v-if="activeTab === 'tokenizer'" class="tab-content">
+                <div class="transform-layout">
+                    <div class="input-section">
+                        <div class="section-header">
+                            <h3><i class="fas fa-layer-group"></i> Tokenizer Visualization <small>{{ tokenizerEngine }}</small></h3>
+                            <p>Paste text to see how different tokenizers segment it.</p>
+                        </div>
+                        <div class="options-grid" style="margin-bottom:8px;">
+                            <label>
+                                Engine
+                                <select v-model="tokenizerEngine" @change="runTokenizer">
+                                    <option value="byte">UTF-8 bytes</option>
+                                    <option value="word">Naive words</option>
+                                    <option value="cl100k">OpenAI: cl100k_base (GPT‑3.5/4)</option>
+                                    <option value="o200k">OpenAI: o200k_base (GPT‑4o)</option>
+                                    <option value="p50k">OpenAI: p50k_base</option>
+                                    <option value="r50k">OpenAI: r50k_base</option>
+                                </select>
+                            </label>
+                        </div>
+                        <textarea 
+                            id="tokenizer-input" 
+                            v-model="tokenizerInput" 
+                            placeholder="Paste text to visualize tokens"
+                            @input="runTokenizer"
+                        ></textarea>
+                    </div>
+
+                    <div class="output-section">
+                        <div class="output-heading">
+                            <h4>
+                                <i class="fas fa-chart-bar"></i> Tokens 
+                                <small>{{ tokenizerTokens.length }} total · {{ tokenizerWordCount }} words · {{ tokenizerCharCount }} chars</small>
+                            </h4>
+                        </div>
+                        <div class="token-tiles" v-if="tokenizerTokens.length" style="display:flex; flex-wrap:wrap; gap:6px;">
+                            <div v-for="(tok, i) in tokenizerTokens" :key="i" class="token-chip" style="background:var(--button-bg); border:1px solid var(--input-border); padding:6px 8px; border-radius:6px; font-family:'Fira Code', monospace;">
+                                <span style="opacity:.75; margin-right:6px;">{{ i }}</span>
+                                <span>{{ tok.text }}</span>
+                                <span v-if="tok.id !== undefined" style="opacity:.6; margin-left:6px;">#{{ tok.id }}</span>
+                            </div>
+                        </div>
+                        <div class="output-instructions" v-else>
+                            <small>Tokens will appear here.</small>
+                        </div>
+                    </div>
+                </div>
+            </div>