build: 打通 FastAPI 与 Vue 最小工程、依赖与数据库连接

后端入口、配置、Redis 与 Alembic 迁移就位；前端 Vite 工程可安装可构建。

backend/alembic/versions/add_agent_ai_replies_toggle_001.py

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+"""
+Copyright 2024-2026 ReplyPier
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+"""add agents.ai_replies_enabled (human-only agents)
+
+Revision ID: add_agent_ai_replies_001
+Revises: purge_mangled_crawl_pages_001
+Create Date: 2026-08-02
+
+Off means the AI never answers on this agent: every chat is queued for the team
+from the customer's first message. Defaults on, so existing agents keep
+answering exactly as before.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = 'add_agent_ai_replies_001'
+down_revision = 'purge_mangled_crawl_pages_001'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        'agents',
+        sa.Column('ai_replies_enabled', sa.Boolean(), server_default=sa.text('true'), nullable=False),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column('agents', 'ai_replies_enabled')