feat(content): add new problem pages, reorganize docs into (problems) subfolders, and update meta display to page

apps/docs/content/(01-linear-structures)/sliding-window/(problems)/643_maximum-average-subarray-i.mdx

@@ -0,0 +1,46 @@
+---
+title: '643. Maximum Average Subarray I'
+description: You are given an integer array nums consisting of n elements, and an integer k
+icon: dot
+topics:
+  - { name: "Array", slug: "array" }
+  - { name: "Sliding Window", slug: "sliding-window" }
+issue: "https://github.com/prdlk/leetcode/issues/55"
+sidebar:
+  label: 'Maximum Average Subarray I'
+  badge: 'Easy'
+---
+
+### Example 1:
+- Input: `nums = [1,12,-5,-6,50,3], k = 4`
+- Output: `12.75000`
+- Explanation: Maximum average is `(12 - 5 - 6 + 50`) / `4 = 51 / 4 = 12.75`
+
+### Example 2:
+- Input: `nums = [5], k = 1`
+- Output: `5.00000`
+
+### Constraints:
+
+- `n == nums.length`
+- `1 <= k <= n <= 10^5`
+- `-10^4 <= nums[i] <= 10^4`
+
+## Solution
+
+```py
+class Solution:
+    def findMaxAverage(self, nums: list[int], k: int) -> float:
+        window_sum = 0
+        for i in range(k):
+            window_sum += nums[i]
+        largest = window_sum
+
+        for right in range(k, len(nums)):
+            left = right - k
+            window_sum -= nums[left]
+            window_sum += nums[right]
+            largest = max(largest, window_sum)
+
+        return largest / k
+```

apps/docs/content/(01-linear-structures)/sliding-window/meta.ts

@@ -1,3 +1,3 @@
 import { defineMeta } from "blume";
 
-export default defineMeta({ title: "Sliding Window", order: 4, icon: "app-window", display: "group" });
+export default defineMeta({ title: "Sliding Window", order: 4, icon: "app-window", display: "page" });