chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/sympy/integrals/benchmarks/bench_integrate.py

@@ -0,0 +1,21 @@
+from sympy.core.symbol import Symbol
+from sympy.functions.elementary.trigonometric import sin
+from sympy.integrals.integrals import integrate
+
+x = Symbol('x')
+
+
+def bench_integrate_sin():
+    integrate(sin(x), x)
+
+
+def bench_integrate_x1sin():
+    integrate(x**1*sin(x), x)
+
+
+def bench_integrate_x2sin():
+    integrate(x**2*sin(x), x)
+
+
+def bench_integrate_x3sin():
+    integrate(x**3*sin(x), x)

backend_service/venv/lib/python3.13/site-packages/sympy/integrals/benchmarks/bench_trigintegrate.py

@@ -0,0 +1,13 @@
+from sympy.core.symbol import Symbol
+from sympy.functions.elementary.trigonometric import sin
+from sympy.integrals.trigonometry import trigintegrate
+
+x = Symbol('x')
+
+
+def timeit_trigintegrate_sin3x():
+    trigintegrate(sin(x)**3, x)
+
+
+def timeit_trigintegrate_x2():
+    trigintegrate(x**2, x)  # -> None