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_hc_favicon_url.py

@@ -0,0 +1,24 @@
+"""Help center favicon URL
+
+Revision ID: add_hc_favicon_001
+Revises: merge_tkt_csat_001
+Create Date: 2026-07-25
+
+Adds a nullable favicon_url to help center settings, mirroring logo_url, so orgs
+can set the browser-tab icon for their public help center from Customization.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "add_hc_favicon_001"
+down_revision = "merge_tkt_csat_001"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("help_center_settings", sa.Column("favicon_url", sa.String(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("help_center_settings", "favicon_url")