feat: 导入增强 + 客户合并 + 同伴自定义 + 性能优化

=== 导入系统全面增强 ===
- 5 Sheet 完整导入：拜访/计划/商机/要客/纪要
- 同访人智能解析：中英文逗号/顿号/分号 → 系统用户UUID + 外部人员TEXT
- 客户自动创建：Excel中不存在的客户自动入库
- 模糊名称匹配：去空格 + 包含关系纠错
- manager_id 修正：导入时用客户分配的经理（非Excel列/非导入人）
- 模板更新：Sheet5「客户经理」→「填报人」，同访人示例含逗号分隔

=== 客户合并功能 ===
- PUT 改名碰撞检测 → 409 + 合并预览
- GET merge-preview / POST merge 端点
- 事务级迁移：Visit/WorkPlan/MiniBusiness/KeyVisit/联系人/分配
- 去重逻辑：联系人(name+phone)、分配(manager+role)
- last_visit_date 取最大值

=== 拜访记录完善 ===
- visits 新增 companion_names TEXT[] 列
- 同访人支持自定义输入（外部人员），el-select allow-create
- 移动端 VisitForm + PC端 ManagerWorkspace 统一
- 周报「客户经理」→「相关人员」（创建人+同访人）
- 纪要「客户经理」→「填报人」
- 删除拜访后重新计算 customer.last_visit_date

=== 客户选择放开 ===
- 客户经理可看到全部客户（不再限自己分配的）
- 拜访时客户下拉返回全量

=== 前端性能优化 ===
- Element Plus 按需加载 (unplugin-vue-components + unplugin-element-plus)
- 周报照片URL并行请求 (Promise.all)
- onMounted 三路并行 (loadReport + dropdowns + AI)
- nginx Cache-Control: immutable for /assets/
- Google Fonts preconnect hints
- 图片上传前 Canvas 压缩 (max 1920px, quality 0.8)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/api/visits.py

@@ -28,6 +28,12 @@ async def _enrich_visit(visit: Visit, db: AsyncSession) -> dict:
         mgr_result = await db.execute(select(User.name).where(User.id == visit.manager_id))
         manager_name = mgr_result.scalar_one_or_none()
 
+    # Resolve companion UUIDs to names
+    companion_names_resolved = list(visit.companion_names or [])
+    if visit.companions:
+        comp_result = await db.execute(select(User.name).where(User.id.in_(visit.companions)))
+        companion_names_resolved = [n for n, in comp_result.all()] + companion_names_resolved
+
     return {
         "id": str(visit.id),
         "customer_id": str(visit.customer_id),
@@ -40,6 +46,8 @@ async def _enrich_visit(visit: Visit, db: AsyncSession) -> dict:
         "communication_content": visit.communication_content,
         "customer_demand": visit.customer_demand,
         "companions": visit.companions,
+        "companion_names": visit.companion_names or [],
+        "companion_names_resolved": companion_names_resolved,
         "photos": visit.photos,
         "manager_id": str(visit.manager_id),
         "manager_name": manager_name,
@@ -137,6 +145,7 @@ async def create_visit(
         communication_content=data.communication_content,
         customer_demand=data.customer_demand,
         companions=data.companions,
+        companion_names=data.companion_names,
         photos=data.photos,
         manager_id=uuid.UUID(current_user["user_id"]),
     )
@@ -245,10 +254,39 @@ async def delete_visit(
     if current_user["role"] == "manager" and str(visit.manager_id) != current_user["user_id"]:
         raise HTTPException(status_code=403, detail="Access denied")
 
+    customer_id = visit.customer_id
+    manager_id = visit.manager_id
+
     # Clean up photos in MinIO
     if visit.photos:
         delete_objects(visit.photos)
 
     await db.delete(visit)
+
+    # Recalculate customer's last_visit_date from remaining visits
+    latest = await db.execute(
+        select(func.max(Visit.visit_date)).where(
+            Visit.customer_id == customer_id,
+        )
+    )
+    new_latest = latest.scalar()
+    cust = await db.get(Customer, customer_id)
+    if cust:
+        if new_latest:
+            cust.last_visit_date = new_latest
+            # Keep the existing manager if date unchanged, or find who made the latest visit
+            latest_visit = await db.execute(
+                select(Visit).where(
+                    Visit.customer_id == customer_id,
+                    Visit.visit_date == new_latest,
+                ).order_by(Visit.created_at.desc()).limit(1)
+            )
+            lv = latest_visit.scalar_one_or_none()
+            if lv:
+                cust.last_visit_manager_id = lv.manager_id
+        else:
+            cust.last_visit_date = None
+            cust.last_visit_manager_id = None
+
     await db.commit()
     return {"detail": "deleted"}