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

apps/docs/content/(05-decision-space)/multi-d-grid-dp/(problems)/64_minimum-path-sum.mdx

@@ -0,0 +1,54 @@
+---
+title: '64. Minimum Path Sum'
+description: Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right, which minimizes the sum of all numbers along its path
+icon: dot
+topics:
+  - { name: "Array", slug: "array" }
+  - { name: "Dynamic Programming", slug: "dynamic-programming" }
+  - { name: "Matrix", slug: "matrix" }
+issue: "https://github.com/prdlk/leetcode/issues/167"
+sidebar:
+  label: 'Minimum Path Sum'
+  badge: 'Medium'
+---
+
+### Example 1:
+- Input: `grid = [[1,3,1],[1,5,1],[4,2,1]]`
+- Output: `7`
+- Explanation: Because the path `1` → `3` → `1` → `1` → `1` minimizes the sum.
+
+### Example 2:
+- Input: `grid = [[1,2,3],[4,5,6]]`
+- Output: `12`
+
+### Constraints:
+
+- `m == grid.length`
+- `n == grid[i].length`
+- `1 <= m, n <= 200`
+- `0 <= grid[i][j] <= 200`
+
+## Solution
+
+```py
+class Solution:
+    def minPathSum(self, grid: list[list[int]]) -> int:
+        if not grid or not grid[0]:
+            return 0
+
+        m = len(grid)
+        n = len(grid[0])
+        dp = [[0 for _ in range(n)] for _ in range(m)]
+
+        for c in range(n):
+            dp[0][c] = dp[0][c - 1] + grid[0][c] if c else grid[0][c]
+
+        for r in range(m):
+            dp[r][0] = dp[r - 1][0] + grid[r][0] if r else grid[r][0]
+
+        for r in range(1, m):
+            for c in range(1, n):
+                dp[r][c] = min(dp[r - 1][c], dp[r][c - 1]) + grid[r][c]
+
+        return dp[-1][-1]
+```