feat(frontend): 添加前端页面模块并实现基本布局

- 新增 chat_page.py、setting_page.py 和 train_page.py 文件，分别实现聊天、设置和微调页面的基本布局
- 添加 main.py 文件，集成所有页面并创建主应用
- 在 requirements.txt 中添加 gradio 依赖

frontend/chat_page.py

@@ -0,0 +1,9 @@
+import gradio as gr
+
+def chat_page():
+    with gr.Blocks() as demo:
+        gr.Markdown("## 聊天")
+        with gr.Row():
+            with gr.Column():
+                pass
+    return demo

frontend/setting_page.py

@@ -0,0 +1,9 @@
+import gradio as gr
+
+def setting_page():
+    with gr.Blocks() as demo:
+        gr.Markdown("## 设置")
+        with gr.Row():
+            with gr.Column():
+                pass
+    return demo

frontend/train_page.py

@@ -0,0 +1,9 @@
+import gradio as gr
+
+def train_page():
+    with gr.Blocks() as demo:
+        gr.Markdown("## 微调")
+        with gr.Row():
+            with gr.Column():
+                pass
+    return demo