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/merge_hc_url_path_001.py

@@ -0,0 +1,50 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+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.
+"""
+
+"""merge the preserved-URL, allow-new-chat and upload-prefix heads
+
+Revision ID: merge_hc_url_path_001
+Revises: add_hc_faq_url_path_001, add_allow_new_chat_001, normalise_upload_prefix_001
+Create Date: 2026-08-10
+
+Three revisions branched off repair_agent_role_seed_001 independently: the
+preserved help-center URLs on this branch, plus allow-new-chat and the upload
+prefix normalisation, which had ALREADY left main with two heads before this
+branch existed. `alembic upgrade head` in scripts/start.sh refuses to pick
+between heads and fails, so the backend crash-loops on start until they are
+rejoined. This no-op merge does that. The revision id is kept short —
+alembic_version.version_num is varchar(32).
+"""
+from alembic import op  # noqa: F401
+import sqlalchemy as sa  # noqa: F401
+
+# revision identifiers, used by Alembic.
+revision = 'merge_hc_url_path_001'
+down_revision = (
+    'add_hc_faq_url_path_001',
+    'add_allow_new_chat_001',
+    'normalise_upload_prefix_001',
+)
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    pass
+
+
+def downgrade() -> None:
+    pass