refactor: 前端架构重构 - 提取 CSS 和逻辑到独立模块

前端重构：
- 删除旧的大体积 Vue 组件（HomeView, FileManage, TextSplit 等）
- 删除旧的 composables（useFormatters, useModels, useProjects）
- 新增 core/, page-logic/, pages/, shared/ 模块化目录结构
- 提取 CSS 到 styles/pages/ 目录
- 添加全局样式 variables.css 和 common.css

后端 API 更新：
- chunks: 语义分割 API 增强
- files: 文件处理 API 更新
- models: 模型管理 API 更新
- questions: 问答管理 API 更新
- database: 数据库连接优化
- semantic_embedding: 语义嵌入服务优化

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/core/database.py

@@ -7,7 +7,7 @@ from contextlib import asynccontextmanager
 from typing import AsyncGenerator
 from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
 from sqlalchemy.orm import DeclarativeBase
-from sqlalchemy import create_engine, event
+from sqlalchemy import create_engine, event, inspect, text
 from sqlalchemy.pool import NullPool
 
 from app.core.config import get_settings
@@ -65,9 +65,28 @@ async def init_db():
     logger.info("Initializing database...")
     async with async_engine.begin() as conn:
         await conn.run_sync(Base.metadata.create_all)
+        await conn.run_sync(_ensure_legacy_columns)
     logger.info("Database initialized successfully")
 
 
+def _ensure_legacy_columns(sync_conn):
+    """Patch legacy tables with newly introduced columns."""
+    inspector = inspect(sync_conn)
+    if "model_configs" not in inspector.get_table_names():
+        return
+
+    columns = {column["name"] for column in inspector.get_columns("model_configs")}
+    if "model_type" in columns:
+        return
+
+    logger.info("Adding missing model_type column to model_configs table")
+    dialect = sync_conn.dialect.name
+    if dialect == "postgresql":
+        sync_conn.execute(text("ALTER TABLE model_configs ADD COLUMN model_type VARCHAR(50) NOT NULL DEFAULT 'chat'"))
+    else:
+        sync_conn.execute(text("ALTER TABLE model_configs ADD COLUMN model_type VARCHAR(50) NOT NULL DEFAULT 'chat'"))
+
+
 async def close_db():
     """Close database connections"""
     logger.info("Closing database connections...")