feat: Add scheduling capabilities for cloud connections

## Feature Request: Add Scheduling Capabilities for Cloud Connections

### Requested by
@aaronsteers (AJ Steers)

### Context
Currently, PyAirbyte's Cloud capabilities allow creating and managing connections, but there's no interface for setting or updating sync schedules. This feature request proposes adding scheduling capabilities that align with Airbyte's API primitives.

### Proposed Interface

Based on investigation of the Airbyte API, the scheduling system uses:
- `schedule_type`: Either `CRON` or `MANUAL`
- `cron_expression`: A standard cron string when using `CRON` schedule type

This is compatible with a simple cron string interface. The proposed interface would:

1. **During Connection Creation** (`CloudWorkspace.deploy_connection()`):
- Add optional `schedule` parameter accepting either:
- `None` (default): Manual sync only
- A cron expression string (e.g., `"0 */6 * * *"` for every 6 hours)
- Internally converts cron string to `AirbyteAPIConnectionSchedule` object

2. **For Existing Connections** (`CloudConnection` class):
- Add `set_schedule(cron_expression: str | None)` method
- `None` sets schedule to MANUAL
- String sets schedule to CRON with the provided expression
- Add `get_schedule()` method returning current schedule info
- These methods are **non-destructive** (unlike config updates)

3. **MCP Tools**:
- `set_cloud_connection_schedule(connection_id, cron_expression)` - marked as non-destructive
- `get_cloud_connection_schedule(connection_id)` - read-only

### Example Usage

```python
import airbyte as ab
from airbyte import cloud

workspace = cloud.CloudWorkspace(...)

# Create connection with schedule
connection = workspace.deploy_connection(
name="My Connection",
source=source,
destination=destination,
schedule="0 */6 * * *", # Every 6 hours
)

# Update schedule on existing connection
connection.set_schedule("0 0 * * *") # Daily at midnight

# Disable automatic syncs
connection.set_schedule(None) # Manual only

# View current schedule
schedule_info = connection.get_schedule()
print(f"Type: {schedule_info.schedule_type}")
print(f"Cron: {schedule_info.cron_expression}")
```

### Implementation Notes

- The Airbyte API already supports scheduling via `AirbyteAPIConnectionSchedule` in `PatchConnectionRequest`
- Cron expressions should be validated before sending to API
- Consider adding helper constants for common schedules (hourly, daily, weekly)
- Documentation should include cron expression examples and link to cron syntax reference

### Related PR
This feature request was created during work on airbytehq/PyAirbyte#841, where an initial `update_schedule()` method was removed to avoid exposing internal API models in the public interface.