update:1.优化 AI 流式生成和进度显示系统 2.新增写作风格系统提示词支持 3.灵感模式功能增强,支持灵感重写 4.设置页面功能扩展，新增Gemini适配器 5.提示词模板系统优化，调整灵感模式提示词

backend/alembic/sqlite/versions/20251227_1700_7899f8d4d839_添加system_prompt字段到settings表.py

@@ -0,0 +1,34 @@
+"""添加system_prompt字段到settings表
+
+Revision ID: 7899f8d4d839
+Revises: a1b2c3d4e5f6
+Create Date: 2025-12-27 17:00:35.440551
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '7899f8d4d839'
+down_revision: Union[str, None] = 'a1b2c3d4e5f6'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('settings', schema=None) as batch_op:
+        batch_op.add_column(sa.Column('system_prompt', sa.Text(), nullable=True, comment='系统级别提示词，每次AI调用都会使用'))
+
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('settings', schema=None) as batch_op:
+        batch_op.drop_column('system_prompt')
+
+    # ### end Alembic commands ###