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/physics/pring.py

@@ -0,0 +1,94 @@
+from sympy.core.numbers import (I, pi)
+from sympy.core.singleton import S
+from sympy.functions.elementary.exponential import exp
+from sympy.functions.elementary.miscellaneous import sqrt
+from sympy.physics.quantum.constants import hbar
+
+
+def wavefunction(n, x):
+    """
+    Returns the wavefunction for particle on ring.
+
+    Parameters
+    ==========
+
+    n : The quantum number.
+        Here ``n`` can be positive as well as negative
+        which can be used to describe the direction of motion of particle.
+    x :
+        The angle.
+
+    Examples
+    ========
+
+    >>> from sympy.physics.pring import wavefunction
+    >>> from sympy import Symbol, integrate, pi
+    >>> x=Symbol("x")
+    >>> wavefunction(1, x)
+    sqrt(2)*exp(I*x)/(2*sqrt(pi))
+    >>> wavefunction(2, x)
+    sqrt(2)*exp(2*I*x)/(2*sqrt(pi))
+    >>> wavefunction(3, x)
+    sqrt(2)*exp(3*I*x)/(2*sqrt(pi))
+
+    The normalization of the wavefunction is:
+
+    >>> integrate(wavefunction(2, x)*wavefunction(-2, x), (x, 0, 2*pi))
+    1
+    >>> integrate(wavefunction(4, x)*wavefunction(-4, x), (x, 0, 2*pi))
+    1
+
+    References
+    ==========
+
+    .. [1] Atkins, Peter W.; Friedman, Ronald (2005). Molecular Quantum
+           Mechanics (4th ed.).  Pages 71-73.
+
+    """
+    # sympify arguments
+    n, x = S(n), S(x)
+    return exp(n * I * x) / sqrt(2 * pi)
+
+
+def energy(n, m, r):
+    """
+    Returns the energy of the state corresponding to quantum number ``n``.
+
+    E=(n**2 * (hcross)**2) / (2 * m * r**2)
+
+    Parameters
+    ==========
+
+    n :
+        The quantum number.
+    m :
+        Mass of the particle.
+    r :
+        Radius of circle.
+
+    Examples
+    ========
+
+    >>> from sympy.physics.pring import energy
+    >>> from sympy import Symbol
+    >>> m=Symbol("m")
+    >>> r=Symbol("r")
+    >>> energy(1, m, r)
+    hbar**2/(2*m*r**2)
+    >>> energy(2, m, r)
+    2*hbar**2/(m*r**2)
+    >>> energy(-2, 2.0, 3.0)
+    0.111111111111111*hbar**2
+
+    References
+    ==========
+
+    .. [1] Atkins, Peter W.; Friedman, Ronald (2005). Molecular Quantum
+           Mechanics (4th ed.).  Pages 71-73.
+
+    """
+    n, m, r = S(n), S(m), S(r)
+    if n.is_integer:
+        return (n**2 * hbar**2) / (2 * m * r**2)
+    else:
+        raise ValueError("'n' must be integer")