feat: 重构草稿箱功能

- 数据库添加 drafts 表存储草稿数据
- 草稿箱独立页面，侧边栏添加入口
- 自动保存间隔可配置（2/5/10/30/60秒）
- 草稿可编辑、发布为正式条目、删除
- 编辑时自动保存到服务器数据库

xian_favor/db.py

@@ -99,6 +99,26 @@ class Database:
                 )
             """)
             
+            # 草稿表
+            cursor.execute("""
+                CREATE TABLE IF NOT EXISTS drafts (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    type TEXT NOT NULL DEFAULT 'text',
+                    title TEXT,
+                    content TEXT,
+                    url TEXT,
+                    source TEXT,
+                    status TEXT DEFAULT 'pending',
+                    priority TEXT DEFAULT 'medium',
+                    due_date TEXT,
+                    note TEXT,
+                    tags TEXT,
+                    is_starred INTEGER DEFAULT 0,
+                    created_at TEXT NOT NULL,
+                    updated_at TEXT NOT NULL
+                )
+            """)
+            
             # 邮件发送记录表
             cursor.execute("""
                 CREATE TABLE IF NOT EXISTS email_logs (
@@ -444,6 +464,109 @@ class Database:
             conn.commit()
             return cursor.rowcount > 0
     
+    # ============ Draft 草稿操作 ============
+    
+    def save_draft(self, type: str = "text", title: str = None, content: str = None,
+                   url: str = None, source: str = None, status: str = "pending",
+                   priority: str = "medium", due_date: str = None, note: str = None,
+                   tags: str = None, is_starred: bool = False) -> int:
+        """保存草稿"""
+        self._ensure_init()
+        now = datetime.now().isoformat()
+        
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("""
+                INSERT INTO drafts (type, title, content, url, source, status, priority, due_date, note, tags, is_starred, created_at, updated_at)
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+            """, (type, title, content, url, source, status, priority, due_date, note, tags, 1 if is_starred else 0, now, now))
+            draft_id = cursor.lastrowid
+            conn.commit()
+            return draft_id
+    
+    def update_draft(self, draft_id: int, **kwargs) -> bool:
+        """更新草稿"""
+        allowed_fields = ['type', 'title', 'content', 'url', 'source', 'status', 'priority', 'due_date', 'note', 'tags', 'is_starred']
+        update_fields = {k: v for k, v in kwargs.items() if k in allowed_fields}
+        
+        if not update_fields:
+            return False
+        
+        now = datetime.now().isoformat()
+        
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT id FROM drafts WHERE id = ?", (draft_id,))
+            if not cursor.fetchone():
+                return False
+            
+            set_clause = ", ".join(f"{k} = ?" for k in update_fields.keys())
+            set_clause += ", updated_at = ?"
+            values = list(update_fields.values()) + [now, draft_id]
+            cursor.execute(f"UPDATE drafts SET {set_clause} WHERE id = ?", values)
+            conn.commit()
+            return True
+    
+    def list_drafts(self, limit: int = 50, offset: int = 0) -> List[Dict[str, Any]]:
+        """列出草稿"""
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT * FROM drafts ORDER BY updated_at DESC LIMIT ? OFFSET ?", (limit, offset))
+            return [dict(row) for row in cursor.fetchall()]
+    
+    def count_drafts(self) -> int:
+        """计算草稿总数"""
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT COUNT(*) as count FROM drafts")
+            return cursor.fetchone()['count']
+    
+    def get_draft(self, draft_id: int) -> Optional[Dict[str, Any]]:
+        """获取单个草稿"""
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT * FROM drafts WHERE id = ?", (draft_id,))
+            row = cursor.fetchone()
+            return dict(row) if row else None
+    
+    def delete_draft(self, draft_id: int) -> bool:
+        """删除草稿"""
+        with self.get_conn() as conn:
+            cursor = conn.cursor()
+            cursor.execute("DELETE FROM drafts WHERE id = ?", (draft_id,))
+            conn.commit()
+            return cursor.rowcount > 0
+    
+    def draft_to_item(self, draft_id: int) -> Optional[int]:
+        """将草稿转为正式条目"""
+        draft = self.get_draft(draft_id)
+        if not draft:
+            return None
+        
+        # 创建条目
+        tags_list = draft['tags'].split(',') if draft['tags'] else []
+        tags_list = [t.strip() for t in tags_list if t.strip()]
+        
+        item_id = self.create_item(
+            type=draft['type'],
+            title=draft['title'],
+            content=draft['content'],
+            url=draft['url'],
+            source=draft['source'],
+            status=draft['status'],
+            priority=draft['priority'],
+            due_date=draft['due_date'],
+            note=draft['note'],
+            tags=tags_list,
+            is_starred=draft['is_starred']
+        )
+        
+        # 删除草稿
+        if item_id:
+            self.delete_draft(draft_id)
+        
+        return item_id
+    
     # ============ Tag 操作 ============
     
     def create_tag(self, name: str, color: str = "#3498db") -> int: