[FEATURE] Add Plivo nodes for SMS and voice calls

Feature Description

Add Flowise tool nodes for Plivo so an agent can send an SMS or place a phone call.

Feature Category

Integration

Problem Statement

Plivo is a CPaaS for SMS and voice. Flowise currently has no Plivo nodes, so an agent cannot send an SMS or place a call through Plivo without building a custom node.

Proposed Solution

I have built two tool nodes plus a credential, following the existing packages/components/nodes/tools pattern

• Plivo Send SMS
• Plivo Make Call
• Plivo API credential (Auth ID and Auth Token)

They call the Plivo REST API, and I have tested both end to end through a Tool Agent flow by sending a real SMS and making a real call which went through. The nodes are implemented and ready to open a PR. Happy to incorporate any changes you suggest.