feat: add AI prompt modal component and Gemini API key

backend/.env

@@ -0,0 +1 @@
+GEMINI_API_KEY=AIzaSyBn_UbFZKCZ18GeMv6l0tSccxDpzRJsbW0

src/components/AIPromptModal.jsx

@@ -0,0 +1,46 @@
+import React, { useState } from 'react';
+
+function AIPromptModal({ isOpen, onClose, onGenerate }) {
+    const [prompt, setPrompt] = useState('');
+
+    if (!isOpen) {
+        return null;
+    }
+
+    const handleGenerate = () => {
+        onGenerate(prompt);
+        setPrompt('');
+        onClose();
+    };
+
+    return (
+        <div className="fixed inset-0 z-50 overflow-hidden flex items-center justify-center">
+            <div className="absolute inset-0 bg-black/20 backdrop-blur-sm transition-opacity" onClick={onClose}></div>
+            <div className="relative theme-surface max-w-lg w-full rounded-lg shadow-2xl p-6 border theme-border">
+                <h2 className="text-lg font-bold theme-text mb-4">Add with AI...</h2>
+                <textarea
+                    value={prompt}
+                    onChange={(e) => setPrompt(e.target.value)}
+                    placeholder="Enter your prompt here..."
+                    className="w-full h-32 bg-transparent border theme-border rounded-lg px-4 py-3 text-sm focus:ring-2 focus:ring-blue-500/20 outline-none transition-all theme-text"
+                />
+                <div className="flex justify-end mt-4">
+                    <button
+                        onClick={onClose}
+                        className="text-sm font-medium theme-text-secondary hover:theme-text mr-4"
+                    >
+                        Cancel
+                    </button>
+                    <button
+                        onClick={handleGenerate}
+                        className="bg-blue-600 hover:bg-blue-700 text-white px-5 py-2 rounded-lg font-medium text-sm transition-all shadow-sm hover:shadow active:scale-95 disabled:opacity-70 disabled:cursor-not-allowed"
+                    >
+                        Generate
+                    </button>
+                </div>
+            </div>
+        </div>
+    );
+}
+
+export default AIPromptModal;