feat: 统一后端分页查询与前端服务层适配

后端新增通用分页模块，为报销单、员工、预算、agent 资产等
端点统一接入分页参数和游标查询，优化 repository 层分页实
现，前端服务层适配分页响应结构，完善预算图表和全局样式，
优化侧边栏和企业选择器组件，引入 Element Plus 插件注册。

server/tests/test_agent_asset_service.py

@@ -156,6 +156,22 @@ def test_agent_asset_service_seeds_all_foundation_asset_types() -> None:
         assert len(service.list_assets(asset_type=AgentAssetType.TASK.value)) >= 3
 
 
+def test_agent_asset_service_supports_backend_pagination() -> None:
+    with build_session() as db:
+        service = AgentAssetService(db)
+
+        page = service.list_assets_page(
+            asset_type=AgentAssetType.RULE.value,
+            page=1,
+            page_size=2,
+        )
+
+        assert len(page.items) <= 2
+        assert page.total >= len(page.items)
+        assert page.page == 1
+        assert page.page_size == 2
+
+
 def test_finance_rules_use_risk_rule_scenario_categories() -> None:
     with build_session() as db:
         service = AgentAssetService(db)

server/tests/test_backend_pagination.py

@@ -0,0 +1,136 @@
+from __future__ import annotations
+
+from collections.abc import Generator
+from datetime import UTC, datetime
+from decimal import Decimal
+
+from fastapi.testclient import TestClient
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from app.api.deps import get_db
+from app.db.base import Base
+from app.main import create_app
+from app.models.employee import Employee
+from app.models.financial_record import ExpenseClaim
+
+
+def build_client() -> tuple[TestClient, sessionmaker[Session]]:
+    engine = create_engine(
+        "sqlite+pysqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(bind=engine)
+    session_factory = sessionmaker(bind=engine, autoflush=False, autocommit=False)
+    app = create_app()
+
+    def override_db() -> Generator[Session, None, None]:
+        db = session_factory()
+        try:
+            yield db
+        finally:
+            db.close()
+
+    app.dependency_overrides[get_db] = override_db
+    return TestClient(app), session_factory
+
+
+def seed_claims(db: Session) -> None:
+    employee = Employee(
+        id="emp-page",
+        employee_no="E-PAGE",
+        name="Page User",
+        email="page-user@example.com",
+        position="Analyst",
+        grade="P4",
+    )
+    db.add(employee)
+    for index in range(3):
+        db.add(
+            ExpenseClaim(
+                id=f"claim-page-{index}",
+                claim_no=f"EXP-PAGE-{index}",
+                employee_id=employee.id,
+                employee_name=employee.name,
+                department_id="dept-page",
+                department_name="Market",
+                project_code=None,
+                expense_type="office",
+                reason=f"Office purchase {index}",
+                location="Shanghai",
+                amount=Decimal("100.00"),
+                currency="CNY",
+                invoice_count=0,
+                occurred_at=datetime(2026, 5, 20 + index, tzinfo=UTC),
+                submitted_at=None,
+                status="draft",
+                approval_stage="draft",
+                risk_flags_json=[],
+                created_at=datetime(2026, 5, 20 + index, tzinfo=UTC),
+                updated_at=datetime(2026, 5, 20 + index, tzinfo=UTC),
+            )
+        )
+    db.commit()
+
+
+def test_expense_claims_support_page_envelope_and_keep_legacy_list() -> None:
+    client, session_factory = build_client()
+    with session_factory() as db:
+        seed_claims(db)
+
+    headers = {"x-auth-username": "E-PAGE", "x-auth-name": "Page User"}
+    legacy_response = client.get("/api/v1/reimbursements/claims", headers=headers)
+    assert legacy_response.status_code == 200
+    assert isinstance(legacy_response.json(), list)
+
+    page_response = client.get(
+        "/api/v1/reimbursements/claims?page=1&page_size=2",
+        headers=headers,
+    )
+
+    assert page_response.status_code == 200
+    payload = page_response.json()
+    assert [key for key in payload if key in {"items", "total", "page", "page_size"}] == [
+        "items",
+        "total",
+        "page",
+        "page_size",
+    ]
+    assert len(payload["items"]) == 2
+    assert payload["total"] == 3
+    assert payload["page"] == 1
+    assert payload["page_size"] == 2
+    assert payload["total_pages"] == 2
+    assert payload["has_next"] is True
+    assert payload["has_previous"] is False
+
+
+def test_employee_directory_supports_backend_pagination() -> None:
+    client, _ = build_client()
+
+    response = client.get("/api/v1/employees?page=2&page_size=10")
+
+    assert response.status_code == 200
+    payload = response.json()
+    assert len(payload["items"]) == 10
+    assert payload["total"] >= 30
+    assert payload["page"] == 2
+    assert payload["page_size"] == 10
+
+
+def test_budget_allocations_support_backend_pagination() -> None:
+    client, _ = build_client()
+
+    response = client.get(
+        "/api/v1/budgets/allocations?page=1&page_size=2",
+        headers={"x-auth-username": "admin", "x-auth-role-codes": "manager"},
+    )
+
+    assert response.status_code == 200
+    payload = response.json()
+    assert len(payload["items"]) <= 2
+    assert payload["total"] >= len(payload["items"])
+    assert payload["page"] == 1
+    assert payload["page_size"] == 2