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/fcm_tokens_per_device_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.
+"""
+
+"""per-device fcm_tokens table, replacing users.fcm_token_web
+
+Revision ID: fcm_tokens_per_device_001
+Revises: add_agent_ai_replies_001
+Create Date: 2026-08-20
+
+The old single column held one push token for the whole account, so signing in
+on a second device overwrote the first one's token and signing out anywhere
+cleared it for every device. Existing tokens are carried over, one row each, so
+already-registered browsers keep receiving pushes across the deploy.
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision = 'fcm_tokens_per_device_001'
+down_revision = 'add_agent_ai_replies_001'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        'fcm_tokens',
+        sa.Column('id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column('user_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column('token', sa.String(), nullable=False),
+        sa.Column('created_at', sa.DateTime(timezone=True),
+                  server_default=sa.text('now()'), nullable=True),
+        sa.Column('updated_at', sa.DateTime(timezone=True),
+                  server_default=sa.text('now()'), nullable=True),
+        sa.ForeignKeyConstraint(['user_id'], ['users.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id'),
+        sa.UniqueConstraint('token', name='uq_fcm_tokens_token'),
+    )
+    op.create_index('ix_fcm_tokens_user_id', 'fcm_tokens', ['user_id'])
+
+    # Carry over the tokens already registered. DISTINCT ON keeps the unique
+    # constraint safe in the unlikely case two accounts share a token — the
+    # most recently updated row wins, which is the one FCM would deliver to.
+    op.execute(
+        """
+        INSERT INTO fcm_tokens (id, user_id, token)
+        SELECT DISTINCT ON (fcm_token_web) gen_random_uuid(), id, fcm_token_web
+        FROM users
+        WHERE fcm_token_web IS NOT NULL AND fcm_token_web <> ''
+        ORDER BY fcm_token_web, updated_at DESC NULLS LAST
+        """
+    )
+
+    op.drop_column('users', 'fcm_token_web')
+
+
+def downgrade() -> None:
+    op.add_column('users', sa.Column(
+        'fcm_token_web', sa.String(), nullable=True))
+    # Only one token per user fits in the old column; keep the newest.
+    op.execute(
+        """
+        UPDATE users u
+        SET fcm_token_web = t.token
+        FROM (
+            SELECT DISTINCT ON (user_id) user_id, token
+            FROM fcm_tokens
+            ORDER BY user_id, created_at DESC
+        ) t
+        WHERE t.user_id = u.id
+        """
+    )
+    op.drop_index('ix_fcm_tokens_user_id', table_name='fcm_tokens')
+    op.drop_table('fcm_tokens')