✨ feat(project)：添加欧拉项目第4、5题解决方案及文档

📝 docs(README)：更新项目描述并添加核心数学理念说明
🔧 chore(pyproject.toml)：更新项目描述信息
♻️ refactor(euler_3.py)：改进质因数分解函数并添加类型注解
💡 docs(readme)：添加第4题数学分析文档和算法说明
✅ test(euler_3.py)：添加主函数测试用例验证质因数分解功能

solutions/0005.smallestMultiple/eular_5.py

@@ -0,0 +1,67 @@
+"""
+2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
+What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
+"""
+
+import math
+import random
+
+
+def is_probable_prime(n: int, trials: int = 10) -> bool:
+    """Miller-Rabin素性测试（快速判断是否为质数）"""
+    if n < 2:
+        return False
+    if n in (2, 3):
+        return True
+    if n % 2 == 0:
+        return False
+
+    # 将 n-1 写成 d * 2^s 的形式
+    d = n - 1
+    s = 0
+    while d % 2 == 0:
+        d //= 2
+        s += 1
+
+    # 测试
+    for _ in range(trials):
+        a = random.randrange(2, n - 1)
+        x = pow(a, d, n)
+        if x == 1 or x == n - 1:
+            continue
+        for _ in range(s - 1):
+            x = pow(x, 2, n)
+            if x == n - 1:
+                break
+        else:
+            return False
+    return True
+
+
+def primes_up_to(n: int) -> list[int]:
+    if n < 2:
+        return []
+    if n == 2:
+        return [2]
+    if n == 3:
+        return [2, 3]
+
+    primes = [2, 3]
+    for i in range(5, n + 1, 2):
+        if is_probable_prime(i):
+            primes.append(i)
+
+    return primes
+
+
+def smallest_multiple(n: int) -> int:
+    result = 1
+    for p in primes_up_to(n):
+        # 找出最大幂次
+        exp = int(math.log(n, p))
+        result *= p**exp
+    return result
+
+
+if __name__ == "__main__":
+    print(smallest_multiple(20))