feat: AI改写功能集成角色数据 + UI优化

- 新增story_characters表和seed_characters.sql种子数据(27个角色)
- AI改写/续写功能注入角色信息(性别/年龄/外貌/性格)
- 首页UI下移避让微信退出按钮
- 个人中心页面布局重构

server/app/routers/story.py

@@ -9,7 +9,7 @@ from typing import Optional, List
 from pydantic import BaseModel
 
 from app.database import get_db
-from app.models.story import Story, StoryNode, StoryChoice
+from app.models.story import Story, StoryNode, StoryChoice, StoryCharacter
 
 router = APIRouter()
 
@@ -214,6 +214,22 @@ async def ai_rewrite_ending(story_id: int, request: RewriteRequest, db: AsyncSes
     if not story:
         raise HTTPException(status_code=404, detail="故事不存在")
     
+    # 获取故事角色
+    char_result = await db.execute(
+        select(StoryCharacter).where(StoryCharacter.story_id == story_id)
+    )
+    characters = [
+        {
+            "name": c.name,
+            "role_type": c.role_type,
+            "gender": c.gender,
+            "age_range": c.age_range,
+            "appearance": c.appearance,
+            "personality": c.personality
+        }
+        for c in char_result.scalars().all()
+    ]
+    
     # 调用 AI 服务
     from app.services.ai import ai_service
     
@@ -222,7 +238,8 @@ async def ai_rewrite_ending(story_id: int, request: RewriteRequest, db: AsyncSes
         story_category=story.category or "未知",
         ending_name=request.ending_name or "未知结局",
         ending_content=request.ending_content or "",
-        user_prompt=request.prompt
+        user_prompt=request.prompt,
+        characters=characters
     )
     
     if ai_result and ai_result.get("content"):
@@ -301,6 +318,22 @@ async def ai_rewrite_branch(
     if not story:
         raise HTTPException(status_code=404, detail="故事不存在")
     
+    # 获取故事角色
+    char_result = await db.execute(
+        select(StoryCharacter).where(StoryCharacter.story_id == story_id)
+    )
+    characters = [
+        {
+            "name": c.name,
+            "role_type": c.role_type,
+            "gender": c.gender,
+            "age_range": c.age_range,
+            "appearance": c.appearance,
+            "personality": c.personality
+        }
+        for c in char_result.scalars().all()
+    ]
+    
     # 将 Pydantic 模型转换为字典列表
     path_history = [
         {"nodeKey": item.nodeKey, "content": item.content, "choice": item.choice}
@@ -315,7 +348,8 @@ async def ai_rewrite_branch(
         story_category=story.category or "未知",
         path_history=path_history,
         current_content=request.currentContent,
-        user_prompt=request.prompt
+        user_prompt=request.prompt,
+        characters=characters
     )
     
     if ai_result and ai_result.get("nodes"):