Design Circular Queue

Design a circular queue (ring buffer) with a fixed capacity `k`. A circular queue reuses freed space at the front, so it never needs to shift elements. - `enQueue(value)` inserts an element; returns `true` if successful, `false` if the queue is full. - `deQueue()` removes an element from the front; returns `true` if successful, `false` if the queue is empty. - `Front()` returns the front element, or `-1` if empty. - `Rear()` returns the last element, or `-1` if empty. - `isEmpty()` returns whether the queue is empty. - `isFull()` returns whether the queue is full. Implement the function `circularQueue(k, operations)` where `k` is the capacity and `operations` is a list of `[op, ...args]`: `["enQueue", v]`, `["deQueue"]`, `["Front"]`, `["Rear"]`, `["isEmpty"]`, `["isFull"]`. Return the list of results, one per operation (use null for operations that return nothing - though every operation here returns a value).