feat: add initial project setup with core PDF tools and utilities

- Implement core PDF manipulation tools (split, merge, convert, etc.)
- Add state management and UI utilities
- Set up build configuration with Vite and TailwindCSS
- Include essential dependencies for PDF processing
- Add gitignore and basic project configuration files

src/js/handlers/toolSelectionHandler.ts

@@ -0,0 +1,41 @@
+import { state } from '../state.js';
+import { dom, switchView, toolTemplates } from '../ui.js';
+import { setupFileInputHandler } from './fileHandler.js';
+import { toolLogic } from '../logic/index.js';
+import { createIcons, icons } from 'lucide';
+
+const SETUP_AFTER_UPLOAD = ['sign-pdf'];
+
+export function setupToolInterface(toolId: any) {
+    window.scrollTo({
+        top: 0,
+        left: 0,
+        behavior: 'instant' as ScrollBehavior
+    });
+    
+    state.activeTool = toolId;
+    dom.toolContent.innerHTML = toolTemplates[toolId]();
+    createIcons({icons});
+    switchView('tool');
+
+    const fileInput = document.getElementById('file-input');
+    const processBtn = document.getElementById('process-btn');
+
+    if (!fileInput && processBtn) {
+        const logic = toolLogic[toolId];
+        if (logic) {
+            const func = typeof logic.process === 'function' ? logic.process : logic;
+            processBtn.onclick = func;
+        }
+    }
+
+    if (toolLogic[toolId] && typeof toolLogic[toolId].setup === 'function') {
+        if (!SETUP_AFTER_UPLOAD.includes(toolId)) {
+            toolLogic[toolId].setup();
+        }
+    }
+
+    if (fileInput) {
+        setupFileInputHandler(toolId);
+    }
+}