feat: add admin customer management

- Add admin customers API endpoints
- Add AdminCustomerService for customer operations
- Enhance customers.html template with management features
- Add customers.js Alpine component
- Add customer list schemas

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/v1/admin/customers.py

@@ -0,0 +1,112 @@
+# app/api/v1/admin/customers.py
+"""
+Customer management endpoints for admin.
+
+Provides admin-level access to customer data across all vendors.
+"""
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_current_admin_api
+from app.core.database import get_db
+from app.services.admin_customer_service import admin_customer_service
+from models.database.user import User
+from models.schema.customer import (
+    CustomerDetailResponse,
+    CustomerListResponse,
+    CustomerMessageResponse,
+    CustomerStatisticsResponse,
+)
+
+router = APIRouter(prefix="/customers")
+
+
+# ============================================================================
+# List Customers
+# ============================================================================
+
+
+@router.get("", response_model=CustomerListResponse)
+def list_customers(
+    vendor_id: int | None = Query(None, description="Filter by vendor ID"),
+    search: str = Query("", description="Search by email, name, or customer number"),
+    is_active: bool | None = Query(None, description="Filter by active status"),
+    skip: int = Query(0, ge=0),
+    limit: int = Query(20, ge=1, le=100),
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+) -> CustomerListResponse:
+    """
+    Get paginated list of customers across all vendors.
+
+    Admin can filter by vendor, search, and active status.
+    """
+    customers, total = admin_customer_service.list_customers(
+        db=db,
+        vendor_id=vendor_id,
+        search=search if search else None,
+        is_active=is_active,
+        skip=skip,
+        limit=limit,
+    )
+
+    return CustomerListResponse(
+        customers=customers,
+        total=total,
+        skip=skip,
+        limit=limit,
+    )
+
+
+# ============================================================================
+# Customer Statistics
+# ============================================================================
+
+
+@router.get("/stats", response_model=CustomerStatisticsResponse)
+def get_customer_stats(
+    vendor_id: int | None = Query(None, description="Filter by vendor ID"),
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+) -> CustomerStatisticsResponse:
+    """Get customer statistics."""
+    stats = admin_customer_service.get_customer_stats(db=db, vendor_id=vendor_id)
+    return CustomerStatisticsResponse(**stats)
+
+
+# ============================================================================
+# Get Single Customer
+# ============================================================================
+
+
+@router.get("/{customer_id}", response_model=CustomerDetailResponse)
+def get_customer(
+    customer_id: int,
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+) -> CustomerDetailResponse:
+    """Get customer details by ID."""
+    customer = admin_customer_service.get_customer(db=db, customer_id=customer_id)
+    return CustomerDetailResponse(**customer)
+
+
+# ============================================================================
+# Toggle Customer Status
+# ============================================================================
+
+
+@router.patch("/{customer_id}/toggle-status", response_model=CustomerMessageResponse)
+def toggle_customer_status(
+    customer_id: int,
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+) -> CustomerMessageResponse:
+    """Toggle customer active status."""
+    result = admin_customer_service.toggle_customer_status(
+        db=db,
+        customer_id=customer_id,
+        admin_email=current_admin.email,
+    )
+    db.commit()
+    return CustomerMessageResponse(message=result["message"])