feat: add list flattening, most frequent element, matrix transpose, and list-to-dict merging

@@ -155,3 +155,27 @@ import random; "#{:06x}".format(random.randint(0, 0xFFFFFF))

all(items[i] <= items[i+1] for i in range(len(items)-1))

```

**Example:** `[1, 2, 3] → True, [3, 2, 1] → False`

## Flatten a nested list (one level)

```python

flattened = [item for sublist in nested_list for item in sublist]

```

**Example:** `[[1, 2], [3, 4]] → [1, 2, 3, 4]`

## Get most frequent element in a list

```python

most_frequent = max(set(items), key=items.count)

```

**Example:** `[1, 2, 3, 1, 2, 1] → 1`

## Transpose a 2D matrix

```python

transposed = [list(row) for row in zip(*matrix)]

```

**Example:** `[[1, 2], [3, 4]] → [[1, 3], [2, 4]]`

## Merge two lists into a dictionary

```python

merged_dict = dict(zip(keys, values))

```

**Example:** `keys=['a', 'b'], values=[1, 2] → {'a': 1, 'b': 2}`